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 A321379 Number of ways to write n as n = a*b*c*d with 1 < a <= b <= c <= d < n. 1
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 2, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,48 COMMENTS This sequence is different from A101638. If p is prime, a(p^k) = A026810(k). - Robert Israel, Nov 08 2018 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE 16 = 2*2*2*2. So a(16) = 1. 24 = 2*2*2*3. So a(24) = 1. MAPLE N:= 100: # for a(1)..a(N) V:= Vector(N): for a from 2 to floor(N^(1/4)) do   for b from a to floor((N/a)^(1/3)) do     for c from b to floor((N/a/b)^(1/2)) do       for d from c to N/(a*b*c) do         V[a*b*c*d]:= V[a*b*c*d]+1 od od od od: convert(V, list); # Robert Israel, Nov 08 2018 CROSSREFS Cf. A026810, A122179, A218320. Sequence in context: A194024 A082786 A101638 * A070141 A088722 A122180 Adjacent sequences:  A321376 A321377 A321378 * A321380 A321381 A321382 KEYWORD nonn AUTHOR Seiichi Manyama, Nov 08 2018 STATUS approved

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Last modified April 25 16:59 EDT 2019. Contains 322461 sequences. (Running on oeis4.)