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 A077763 Number of ways of pairing the odd squares of the numbers 1 to n with the even squares of the numbers n+1 to 2n such that each pair sums to a prime. 2
 1, 1, 0, 1, 2, 0, 1, 1, 2, 2, 0, 1, 7, 2, 10, 14, 38, 6, 118, 62, 80, 144, 604, 711, 6201, 4005, 8570, 14544 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS The Mathematica program uses backtracking to find all solutions. The Print statement can be uncommented to print all solutions. The product of this sequence and A077764 gives A077762. LINKS EXAMPLE a(5)=2 because two pairings are possible: 1+36=37, 9+100=109, 25+64=89 and 1+100=101, 9+64=73, 25+36=61 MATHEMATICA try[lev_] := Module[{j}, If[lev>n, (*Print[soln]; *) cnt++, For[j=1, j<=Length[s[[lev]]], j++, If[ !MemberQ[soln, s[[lev]][[j]]], soln[[lev]]=s[[lev]][[j]]; try[lev+2]; soln[[lev]]=0]]]]; maxN=28; For[lst1={1}; n=2, n<=maxN, n++, s=Table[{}, {n}]; For[i=1, i<=n, i=i+2, For[j=n+1, j<=2n, j++, If[PrimeQ[i^2+j^2], AppendTo[s[[i]], j]]]]; soln=Table[0, {n}]; cnt=0; try[1]; AppendTo[lst1, cnt]]; lst1 CROSSREFS Cf. A077762, A077764. Sequence in context: A127506 A007968 A236532 * A030218 A281388 A127440 Adjacent sequences:  A077760 A077761 A077762 * A077764 A077765 A077766 KEYWORD hard,nonn AUTHOR T. D. Noe, Nov 15 2002 STATUS approved

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Last modified October 22 09:57 EDT 2018. Contains 316433 sequences. (Running on oeis4.)