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A116913
Inverse Moebius transform of pentagonal numbers.
3
1, 6, 13, 28, 36, 69, 71, 120, 130, 186, 177, 301, 248, 363, 378, 496, 426, 663, 533, 798, 734, 897, 783, 1245, 961, 1254, 1210, 1547, 1248, 1914, 1427, 2016, 1806, 2148, 1926, 2821, 2036, 2685, 2522, 3270, 2502, 3702, 2753, 3801, 3510, 3939, 3291, 5053, 3648
OFFSET
1,2
LINKS
FORMULA
a(n) = Sum_{d|n} d*(3*d-1)/2.
G.f.: Sum_{k>=1} k*(3*k-1)/2*x^k/(1 - x^k). - Ilya Gutkovskiy, May 23 2017
MATHEMATICA
Table[Sum[d*(3d - 1)/2, {d, Divisors[n]}], {n, 101}] (* Indranil Ghosh, May 23 2017 *)
PROG
(PARI) a(n) = sumdiv(n, d, d*(3*d-1)/2); \\ Michel Marcus, Mar 25 2015
CROSSREFS
Cf. A000326 (pentagonal numbers).
Inverse Moebius transforms of polygonal numbers: A007437 (k=3), A001157 (k=4), this sequence (k=5), A278945 (k=6), A278947 (k=7).
Sequence in context: A301687 A173559 A086224 * A016071 A086652 A159694
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Mar 19 2006
EXTENSIONS
More terms from Michel Marcus, Mar 25 2015
STATUS
approved