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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A007650 Number of set-like atomic species of degree n.
(Formerly M2227)
2
0, 1, 1, 1, 3, 1, 6, 1, 10, 4, 12, 1, 33, 1, 29, 13, 64, 1, 100, 1, 156, 30, 187, 1, 443, 10, 476, 78, 877, 1, 1326, 1, 2098, 188, 2745, 36, 5203, 1, 6408, 477, 11084, 1, 15687, 1, 24709, 1241, 33249, 1, 57432, 27, 74529, 2746, 120984, 1, 168668, 194, 264075, 6409, 356624, 1, 579893, 1, 768857, 14898, 1214452, 483, 1669060, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

REFERENCES

G. Labelle and P. Leroux, Identities and enumeration: weighting connected components, Abstracts Amer. Math. Soc., 15 (1994), Meeting #896.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Joerg Arndt, Table of n, a(n) for n = 0..100

S. Eberhart & N. J. A. Sloane, Correspondence, 1977

G. Labelle and P. Leroux, Identities and enumeration: weighting connected components, Abstracts Amer. Math. Soc., 15 (1994), Meeting #896. (Annotated scanned copy)

G. Labelle and P. Leroux, An extension of the exponential formula in enumerative combinatorics, The Electronic Journal of Combinatorics, Volume 3, Issue 2 (1996) (The Foata Festschrift volume), Research Paper #R12.

N. J. A. Sloane, Transforms

FORMULA

Inverse Euler Transform of A007649. Define c(n): c(0)=0. c(k)=A007649(k), k>0. a=MOEBIUSi(c)-c. - Christian G. Bower, Feb 23 2006

MATHEMATICA

NN = 66;  va = Array[0&, NN]; va[[1]] = 0; va[[2]] = 1; vm = Array[0&, NN]; vm[[1]] = 1; vm[[2]] = 1; For[n = 2, n <= NN - 1, n++, va[[n + 1]] = DivisorSum[n , vm[[#+1]]&]; vm[[n+1]] = 1/n*Sum[DivisorSum[k, #*va[[#+1]] &]*vm[[n-k+1]], {k, 1, n}]]; va (* Jean-Fran├žois Alcover, Dec 01 2015, adapted from Joerg Arndt's PARI script in A007649 *)

PROG

(PARI) /* see A007649 */

CROSSREFS

Cf. A005226, A007649.

Sequence in context: A304236 A145063 A202851 * A236540 A339384 A165552

Adjacent sequences:  A007647 A007648 A007649 * A007651 A007652 A007653

KEYWORD

nonn

AUTHOR

Simon Plouffe

EXTENSIONS

Added more terms, Joerg Arndt, Jul 30 2012

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 10 21:08 EDT 2021. Contains 343780 sequences. (Running on oeis4.)