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pronic numbers
The  $n$-th pronic numbers is equal to  $n(n+1)$  and is thus twice the  $n$-th triangular number.

Pronic numbers are also called oblong numbers, rectangular numbers or heteromecic numbers.

The sum of the reciprocals of pronic numbers is 1.

Pronic numbers cannot be squares, but they can be triangular numbers. For example, 242556 = 492×493 = 696×697/2 = T696.

The first pronic numbers are 2, 6, 12, 20, 30, 42, 56, 72, 90, 110, 132, 156, 182, 210, 240, 272, 306, 342, 380, 420, 462, 506, 552, 600 more terms

Pronic numbers can also be... (you may click on names or numbers and on + to get more values)

ABA 72 2450 83232 + 3765344262050 aban 12 20 30 + 999999000000 abundant 12 20 30 + 49991970 Achilles 72 83232 456300 + 3331356865200 admirable 12 20 30 + 67100672 alternating 12 30 56 + 892187030 amenable 12 20 56 + 999856020 apocalyptic 506 650 702 + 29756 arithmetic 20 30 42 + 9995082 binomial 20 56 210 + 323015470680 c.pentagonal 8556 12337656 17790891306 25654452925506 cake 42 2635752 Catalan 42 132 congruent 20 30 56 + 9988760 constructible 12 20 30 + 4295032832 Cunningham 342 1332 Curzon 30 90 210 + 198965130 d-powerful 132 2352 6972 + 9837632 deficient 110 182 506 + 9969806 dig.balanced 12 42 56 + 199586256 droll 72 240 Duffinian 2450 2827442 eban 30 42 56 + 64000040000006 economical 16256 16512 65792 + 19514306 equidigital 16256 16512 65792 + 19514306 eRAP 20 9808030260 13915387332 573205709712 esthetic 12 56 210 + 78987656 evil 12 20 30 + 999982506 Friedman 1260 86142 132860 + 792990 frugal 261632 12841472 19127502 + 976531250 gapful 110 132 240 + 99997934400 Gilda 110 Giuga 30 1722 2214408306 happy 1122 1332 5112 + 9982440 harmonic 2970 8190 Harshad 12 20 30 + 9999900000 heptagonal 342 711635652 hexagonal 7140 8239770 9508687656 10973017315470 highly composite 12 240 1260 + 4324320 hoax 650 702 2352 + 99830072 iban 12 20 42 + 777042 idoneal 12 30 42 + 462 inconsummate 272 552 650 + 995006 interprime 12 30 42 + 99950006 Jordan-Polya 12 72 240 junction 210 420 812 + 99630342 Kaprekar 82656 katadrome 20 30 42 + 96410 Leyland 65792 4295032832 Lynch-Bell 12 132 46872 613872 magic 870 magnanimous 12 20 30 + 992 metadrome 12 56 156 modest 812 6162 14042 + 1840023920 Moran 42 156 nialpdrome 20 30 42 + 99999990000000 nude 12 132 1122 + 482614992 O'Halloran 12 20 156 + 420 oban 12 20 30 + 930 odious 42 56 110 + 999792780 palindromic 272 6006 289982 + 250087292780052 pancake 56 1892 64262 + 98757155839232 panconsummate 12 20 72 pandigital 156 210 1190 + 9854632170 partition 30 42 56 pentagonal 12 210 116622 + 186039792969240 pernicious 12 20 42 + 9976122 Perrin 12 90 persistent 2965837140 7932485160 8264537190 + 97384252160 plaindrome 12 56 156 + 44444455555556 powerful 72 83232 456300 + 127910863523592 practical 12 20 30 + 9988760 prim.abundant 12 20 30 + 81947756 primorial 30 210 510510 pseudoperfect 12 20 30 + 4294901760 repunit 156 3906 97656 + 596046447753906 Ruth-Aaron 154842 39494940 433451580 + 98470753800 Saint-Exupery 17112695040 3084099701760 self 20 42 110 + 999350156 sliding 20 110 650 + 100000010000000 Smith 2970 8372 12656 + 99770132 sphenic 30 42 110 + 99470702 straight-line 210 420 super Niven 12 20 30 + 40000200000 super-d 462 1056 1190 + 9900462 superabundant 12 240 1260 4324320 tau 12 56 72 + 999539840 taxicab 262656 2987712 1402390152 + 688403231516160 tetrahedral 20 56 7140 1414910 tetranacci 56 triangular 210 7140 242556 + 372759573255306 uban 12 20 30 + 96040049000006 Ulam 72 182 1406 + 9969806 undulating 272 unprimeable 1260 1332 1640 + 9995082 untouchable 210 306 342 + 999000 upside-down 4556 8372 849162 + 886422 vampire 1260 1178926560 1287553806 + 3482593182 wasteful 12 20 30 + 9995082 Zuckerman 12 132 1332 + 123132312 Zumkeller 12 20 30 + 99540 zygodrome 1122 4422 9900 + 99999990000000