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A342808 Smallest k such that the k-th tetrahedral number is divisible by exactly n tetrahedral numbers. 0
1, 2, 6, 4, 8, 28, 14, 48, 55, 98, 154, 54, 495, 1034, 504, 559, 208, 440, 2078, 2000, 350, 3519, 6578, 2574, 5983, 2924, 21734, 25023, 11934, 30303, 120175, 81718, 11438, 73150, 71630, 43470, 50048, 511784, 371448, 37960, 1478048, 391950, 812174, 393470, 217854, 576288 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..46.

EXAMPLE

a(6) = 28 as the 28th tetrahedral number, binomial(28+2, 3) = 4060, is divisible by 6 tetrahedral numbers namely 1, 4, 10, 20, 35 and 4060.

PROG

(PARI) first(n) = { my(res = vector(n), todo = n); for(i = 1, oo, c = f(i); if(c <= n && res[c] == 0, res[c] = i; todo--; if(todo <= 0, return(res)))) }

f(n) = my(d = divisors(binomial(n + 2, 3))); #select(x -> istetra(x), d) istetra(n)= my(k = sqrtnint(6*n, 3)); binomial(k + 2, 3) == n

CROSSREFS

Cf. A000292, A076983, A318556, A319788.

Sequence in context: A204906 A097265 A324651 * A201895 A192408 A074208

Adjacent sequences:  A342805 A342806 A342807 * A342809 A342810 A342811

KEYWORD

nonn

AUTHOR

David A. Corneth, Mar 22 2021

STATUS

approved

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Last modified June 17 13:43 EDT 2021. Contains 345080 sequences. (Running on oeis4.)