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 A228571 The backwards antidiagonal sums of triangle A228570. 1
 1, 0, 1, 0, 1, 1, 1, 1, 1, 2, 2, 2, 3, 3, 5, 4, 7, 6, 10, 10, 14, 15, 20, 24, 30, 35, 45, 53, 69, 79, 104, 120, 157, 184, 236, 281, 356, 431, 540, 656, 821, 1001, 1252, 1525, 1908, 2328, 2909, 3557, 4434, 5436, 6762 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,10 COMMENTS The a(n) equal the backwards antidiagonal sums of triangle A228570. LINKS FORMULA a(n) = sum(A228570(n-k, n-2*k), k=0..floor(n/2)). G.f.: (1/2)*(1/(1-x^2-x^5) + (1+x^2+x^5)/(1-x^4-x^10)). MAPLE f := x -> (1/((1-x^2-x^5)) + (1+x^2+x^5)/(1-x^4-x^10))/2 : seq(coeff(series(f(x), x, n+1), x, n), n=0..50);  # End first program a := proc(n): (A001687(n+1) + x(n) + x(n-2) + x(n-5))/2 end: A001687 := proc(n) option remember: if n=0 then 0 elif n=1 then 1 elif n=2 then 0 elif n=3 then 1 elif n=4 then 0 else procname(n-2) + procname(n-5) fi: end: x := proc(n) local x: if n <0 then return(0) fi: if type(n, even) then A001687((n+2)/2) else 0 fi: end: seq(a(n), n=0..50); # End second program CROSSREFS Cf. A228570, A102543, A192928, A001687. Sequence in context: A055256 A295630 A029147 * A224908 A029097 A210955 Adjacent sequences:  A228568 A228569 A228570 * A228572 A228573 A228574 KEYWORD nonn,easy AUTHOR Johannes W. Meijer, Aug 26 2013 STATUS approved

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Last modified January 25 05:31 EST 2021. Contains 340416 sequences. (Running on oeis4.)