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A099950
Number of 2-sparse nonoverlapping partitions of n.
0
1, 1, 1, 2, 4, 10, 27, 80, 255, 870, 3155, 12100, 48871, 207162, 918944, 4254690, 20513838, 102784942, 534205629, 2875098840, 15999114433, 91923562922, 544606671776, 3323112062994, 20860869818386, 134585869671342
OFFSET
0,4
PROG
(PARI) {a(n)=local(A); if(n<0, 0, A=O(x^0); for(i=0, n\2, A=(1+x)/(1-x^2*subst(A, x, x/(1-x)))); polcoeff(A, n))} /* Michael Somos, Sep 22 2005 */
CROSSREFS
Sequence in context: A148106 A291210 A340635 * A121690 A138356 A287693
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Nov 12 2004
STATUS
approved