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 A121081 Number of partitions of n into parts with at most one 1 and at most one 2. 2
 1, 1, 2, 2, 3, 5, 6, 8, 11, 14, 18, 24, 30, 38, 49, 61, 76, 96, 118, 146, 181, 221, 270, 331, 401, 486, 589, 709, 852, 1025, 1225, 1463, 1746, 2075, 2463, 2922, 3453, 4077, 4808, 5656, 6644, 7798, 9130, 10678, 12475, 14547, 16942, 19714, 22898, 26570, 30798 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS a(n) is also the number of partitions of n with no part equal to 2 or 4. [From Shanzhen Gao, Oct 28 2010] LINKS FORMULA a(n) = A121659(n) + A008483(n-3) for n>2. - Reinhard Zumkeller, Aug 14 2006 G.f.: (1+x)*(1+x^2)/Product_{k>=3} (1-x^k). - Vladeta Jovovic, Aug 13 2006 a(n) = A000041(n)-A000041(n-2)-A000041(n-4)+A000041(n-6), n>5. - Vladeta Jovovic, Aug 13 2006 Given by p(n)-p(n-2)-p(n-4)+p(n-6) where p(n)=A000041(n). - Shanzhen Gao, Oct 28 2010 a(n) ~ exp(Pi*sqrt(2*n/3)) * Pi^2 / (3^(3/2) * n^2). - Vaclav Kotesovec, Jun 02 2018 EXAMPLE a(8)=#{8,7+1,6+2,5+3,5+2+1,4+4,4+3+1,3+3+2}=8; a(9)=#{9,8+1,7+2,6+3,6+2+1,5+4,5+3+1,4+4+1,4+3+2,3+3+3,3+3+2+1}=11. CROSSREFS Cf. A027336. Sequence in context: A052337 A308858 A192432 * A330952 A118399 A278298 Adjacent sequences: A121078 A121079 A121080 * A121082 A121083 A121084 KEYWORD nonn AUTHOR Reinhard Zumkeller, Aug 11 2006 STATUS approved

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Last modified February 6 01:28 EST 2023. Contains 360091 sequences. (Running on oeis4.)