Search: id:A001475
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%I A001475 M1449 N0573
%S A001475 1,2,5,13,38,116,382,1310,4748,17848,70076,284252,1195240,5174768,
%T A001475 23103368,105899656,498656912,2404850720,11879332048,59976346448
%N A001475 a(n) = a(n-1) + n a(n-2).
%C A001475 a(n) = number of partitions of [n] in which the block containing 1 is 
               of length <= 3 and all other blocks are of length <= 2. Example: 
               a(4)=13 counts all 15 partitions of [4] except 1234 and 1/234. - 
               David Callan (callan(AT)stat.wisc.edu), Jul 22 2008
%D A001475 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A001475 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A001475 J. Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 
               86 (divided by 2).
%F A001475 E.g.f.: 1/2*(1+x)*exp(x+1/2*x^2)-1/2. - Vladeta Jovovic (vladeta(AT)eunet.rs), 
               Nov 04 2003
%Y A001475 Equals (1/2) A000085(n+1). Cf. A001189, A013989.
%Y A001475 Sequence in context: A064384 A148302 A149857 this_sequence A149858 A148303 
               A148304
%Y A001475 Adjacent sequences: A001472 A001473 A001474 this_sequence A001476 A001477 
               A001478
%K A001475 nonn
%O A001475 1,2
%A A001475 N. J. A. Sloane (njas(AT)research.att.com).

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