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 A358542 a(n) is the smallest number with exactly n divisors that are tetrahedral numbers. 4
 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 (list; graph; refs; listen; history; text; internal format)
 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 a(n) = my(k=1); while (sumdiv(k, d, istetrah(d)) != n, k++); k; \\ Michel Marcus, Nov 21 2022 CROSSREFS Cf. A000292, A005179, A130317, A279495, A358543, A358544. Sequence in context: A355073 A054751 A189873 * A359656 A329459 A143650 Adjacent sequences: A358539 A358540 A358541 * A358543 A358544 A358545 KEYWORD nonn AUTHOR Ilya Gutkovskiy, Nov 21 2022 EXTENSIONS a(20)-a(22) from Michel Marcus, Nov 21 2022 a(23)-a(30) from Jinyuan Wang, Nov 28 2022 a(31) from Martin Ehrenstein, Dec 02 2022 a(32) and a(33) from Lucas A. Brown, Dec 14 2022 STATUS approved

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Last modified September 30 02:05 EDT 2023. Contains 365781 sequences. (Running on oeis4.)