A358859 a(n) is the smallest n-gonal number divisible by exactly n n-gonal numbers.

6, 36, 210, 4560, 6426, 326040, 4232250, 1969110, 296676380, 4798080, 166289760, 73765692000, 712750500, 50561280, 33944067893736, 2139168754800, 4292572951800, 1414764341760, 72461756727360, 180975331456920, 1870768457500800, 5498331930000, 153698278734000

Offset

3,1

Comments

The corresponding indices of n-gonal numbers are 3, 6, 12, 48, 51, 330, 1100, 702, ...

Links

Table of n, a(n) for n=3..25.

Eric Weisstein's World of Mathematics, Polygonal Number

Index entries for sequences related to divisors of numbers

Example

a(5) = 210, because 210 is a pentagonal number that has 5 pentagonal divisors {1, 5, 35, 70, 210} and this is the smallest such number.

Prog

(PARI) a(n) = if(n<3, return()); for(k=1, oo, my(t=(k*(n*k - n - 2*k + 4))\2); if(sumdiv(t, d, ispolygonal(d, n)) == n, return(t))); \\ Daniel Suteu, Dec 04 2022

Crossrefs

Cf. A005179, A076983, A358539, A358860, A358861.

Sequence in context: A357027 A357093 A357029 * A357091 A268454 A171280

Adjacent sequences: A358856 A358857 A358858 * A358860 A358861 A358862

Keyword

nonn

Author

Ilya Gutkovskiy, Dec 03 2022

Extensions

a(11)-a(25) from Daniel Suteu, Dec 04 2022

Status

approved