cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A131693 Numbers n such that S(n) = 0, where S(n) = (S(n-1) + A000040(n+1))*(-1)^n; S(0)=0, n >= 1.

Original entry on oeis.org

10, 14, 18, 4290, 4392, 4434, 4440, 4456, 4480, 48596, 48620, 48744, 49540, 49544, 49722, 55058, 55078, 55200, 56466, 56474, 60110, 60128, 60462, 60750, 61328, 61486, 62114, 62758, 62770, 62974, 62992, 63022, 63076, 63094, 63272, 63802
Offset: 1

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Author

Manuel Valdivia, Oct 03 2007

Keywords

Comments

Or, with A065091(odd primes), numbers n such that S(n) = 0, where S(n) = (S(n-1) + A065091(n))*(-1)^n; S(0)=0, n >= 1.

Examples

			S(9) = (..((0+3)*-1)+5)*1)+7)*-1)+11)*1)+13)*-1)+17)*1)+19)*-1)+23)*1)+29)*-1 = -31, S(10)=(-31 + 31)*1 = 0, hence 10 is a term.
S(13) = (..((0+3)*-1)+5)*1)+7)*-1)+11)*1)+13)*-1)+17)*1)+19)*-1)+23)*1)+29)*-1)+31)*1)+37)*-1)+41)*1)+43)*-1 = -47, S(14)=(-47 + 47)*1 = 0, hence 14 is a term.
		

Crossrefs

Programs

  • Mathematica
    S=0;a=0; Do[S=(S+Prime[n+1])*(-1)^n; If[S==0,a++; Print[a," ",n]], {n, 1, 10^8, 1}]
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