The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A063966 Number of Abelian groups of order <= n. 8
 1, 2, 3, 5, 6, 7, 8, 11, 13, 14, 15, 17, 18, 19, 20, 25, 26, 28, 29, 31, 32, 33, 34, 37, 39, 40, 43, 45, 46, 47, 48, 55, 56, 57, 58, 62, 63, 64, 65, 68, 69, 70, 71, 73, 75, 76, 77, 82, 84, 86, 87, 89, 90, 93, 94, 97, 98, 99, 100, 102, 103, 104, 106, 117, 118, 119, 120, 122 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Vaclav Kotesovec, Table of n, a(n) for n = 1..10000 B. Horvat, G. Jaklic and T. Pisanski, On the number of Hamiltonian groups, arXiv:math/0503183 [math.CO], 2005. Eric Weisstein's World of Mathematics, Abelian Group FORMULA a(n) ~ c * n, where c = A021002 = Product_{k>=2} Zeta(k). - Vaclav Kotesovec, Oct 26 2019 MAPLE with(combinat): readlib(ifactors): total := 0: for n from 1 to 100 do ans := 1: for i from 1 to nops(ifactors(n)[2]) do ans := ans*numbpart(ifactors(n)[2][i][2]) od: printf(`%d, `, total+ans): total := total+ans: od: MATHEMATICA Accumulate[Table[FiniteAbelianGroupCount[n], {n, 1, 200}]] (* Geoffrey Critzer, Dec 28 2014 *) CROSSREFS Partial sums of A000688. Cf. A063756. Sequence in context: A094180 A116545 A140661 * A123030 A284836 A267300 Adjacent sequences:  A063963 A063964 A063965 * A063967 A063968 A063969 KEYWORD nonn AUTHOR Ahmed Fares (ahmedfares(AT)my-deja.com), Sep 04 2001 EXTENSIONS More terms from James A. Sellers, Sep 26 2001 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified November 24 01:49 EST 2020. Contains 338603 sequences. (Running on oeis4.)