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A069972 a(n) = Sum_{d|2*n,d+1|2*n} d. 1
1, 1, 3, 1, 1, 6, 1, 1, 3, 5, 1, 6, 1, 1, 8, 1, 1, 6, 1, 5, 9, 1, 1, 6, 1, 1, 3, 8, 1, 15, 1, 1, 3, 1, 1, 14, 1, 1, 3, 5, 1, 12, 1, 1, 17, 1, 1, 6, 1, 5, 3, 1, 1, 6, 11, 8, 3, 1, 1, 15, 1, 1, 9, 1, 1, 17, 1, 1, 3, 5, 1, 14, 1, 1, 8, 1, 1, 18, 1, 5, 3, 1, 1, 19, 1, 1, 3, 1, 1, 24, 14, 1, 3, 1, 1, 6, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
LINKS
FORMULA
G.f.: (conjectured) Sum_{n>=1} n*x^(n*(n+1)/2)/(1-x^(n*(n+1)/2)). - Joerg Arndt, Jan 30 2011
PROG
(PARI) A069972(n) = { n = 2*n; sumdiv(n, d, if(!(n%(1+d)), d, 0)); }; \\ Antti Karttunen, Mar 02 2023
CROSSREFS
Cf. A007862.
Sequence in context: A364113 A324284 A300791 * A115017 A088439 A162315
KEYWORD
easy,nonn
AUTHOR
Vladeta Jovovic, Apr 29 2002
STATUS
approved

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Last modified March 28 10:55 EDT 2024. Contains 371241 sequences. (Running on oeis4.)