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A358542

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

1, 4, 56, 20, 120, 280, 560, 840, 1680, 10920, 9240, 18480, 55440, 120120, 240240, 314160, 628320, 1441440, 2282280, 7225680, 4564560, 9129120, 13693680, 27387360, 54774720, 68468400, 77597520, 136936800, 155195040, 310390080, 465585120, 775975200, 1163962800

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OFFSET

1,2

LINKS

Lucas A. Brown, Table of n, a(n) for n = 1..37

Lucas A. Brown, Python program.

Eric Weisstein's World of Mathematics, Tetrahedral Number

Index entries for sequences related to divisors of numbers

EXAMPLE

a(3) = 56 because 56 has 3 tetrahedral divisors {1, 4, 56} and this is the smallest such number.

PROG

(PARI) istetrah(n) = my(k=sqrtnint(6*n, 3)); k*(k+1)*(k+2)==6*n; \\ A000292