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.

A355819 Dirichlet inverse of A270419, denominator of the rational number obtained when the exponents in prime factorization of n are reinterpreted as alternating binary sums (A065620).

Original entry on oeis.org

1, -1, -1, 0, -1, 1, -1, -1, 0, 1, -1, 0, -1, 1, 1, 2, -1, 0, -1, 0, 1, 1, -1, 1, 0, 1, -2, 0, -1, -1, -1, -8, 1, 1, 1, 0, -1, 1, 1, 1, -1, -1, -1, 0, 0, 1, -1, -2, 0, 0, 1, 0, -1, 2, 1, 1, 1, 1, -1, 0, -1, 1, 0, 12, 1, -1, -1, 0, 1, -1, -1, 0, -1, 1, 0, 0, 1, -1, -1, -2, 4, 1, -1, 0, 1, 1, 1, 1, -1, 0, 1, 0, 1, 1, 1, 8
Offset: 1

Views

Author

Antti Karttunen, Jul 19 2022

Keywords

Comments

Multiplicative because A270419 is.

Crossrefs

Cf. also A355826.

Programs

  • PARI
    A065620(n, c=1) = sum(i=0, logint(n+!n, 2), if(bittest(n, i), (-1)^c++<A065620
    A270419(n) = {n=factor(n); n[, 2]=apply(A065620, n[, 2]); denominator(factorback(n)); }; \\ From A270419
    memoA355819 = Map();
    A355819(n) = if(1==n,1,my(v); if(mapisdefined(memoA355819,n,&v), v, v = -sumdiv(n,d,if(dA270419(n/d)*A355819(d),0)); mapput(memoA355819,n,v); (v)));

Formula

a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, dA270419(n/d) * a(d).