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A318556 a(n) is the number of lesser tetrahedral numbers that divide the n-th tetrahedral number. 3
0, 1, 1, 3, 1, 2, 2, 4, 1, 4, 1, 2, 2, 6, 4, 2, 1, 4, 3, 6, 1, 2, 4, 4, 1, 4, 1, 5, 1, 4, 2, 2, 2, 6, 3, 2, 1, 4, 4, 6, 1, 2, 3, 6, 1, 2, 3, 7, 2, 4, 1, 2, 2, 11, 8, 3, 1, 4, 2, 4, 1, 4, 11, 6, 1, 2, 1, 5, 2, 8, 2, 2, 1, 4, 4, 4, 1, 4, 5, 5, 1, 2, 3, 5, 1, 2, 2, 7, 3, 8, 1, 2, 1, 4, 4, 3, 1, 9 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

David A. Corneth, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = Sum_{m=1..n-1} [0 = A000292(n) mod A000292(m)]. Here [] is the Iverson bracket function.

EXAMPLE

t(4) is 20 and 20 is divisible by t(1)=1, t(2)=4 and t(3)=10, so a(4)=3.

PROG

(PARI) t(n) = n*(n+1)*(n+2)/6;

a(n) = my(tn=n*(n+1)*(n+2)/6); sum(k=1, n-1, (tn % t(k)) == 0); \\ Michel Marcus, Sep 27 2018

CROSSREFS

Cf. A000292.

Sequence in context: A029336 A211939 A010280 * A292148 A125266 A002016

Adjacent sequences:  A318553 A318554 A318555 * A318557 A318558 A318559

KEYWORD

nonn

AUTHOR

Torlach Rush, Aug 28 2018

STATUS

approved

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Last modified September 24 17:57 EDT 2022. Contains 356946 sequences. (Running on oeis4.)