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A358539

a(n) is the smallest number with exactly n divisors that are n-gonal numbers.

6, 36, 210, 1260, 6426, 3360, 351000, 207900, 3749460, 1153152, 15036840, 204204000, 213825150, 11737440, 91797866160, 1006485480, 2310808500, 4966241280, 22651328700, 325269404460, 14266470332400, 11203920000, 256653797400, 45843256859400, 59207908359600, 46822406400

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OFFSET

3,1

LINKS

Table of n, a(n) for n=3..28.

Lucas A. Brown, Python program.

Eric Weisstein's World of Mathematics, Polygonal Number

Index entries for sequences related to divisors of numbers

EXAMPLE

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

PROG

(PARI) a(n) = my(k=1); while (sumdiv(k, d, ispolygonal(d, n)) != n, k++); k; \\ Michel Marcus, Nov 21 2022