A296210 Characteristic function for A104210: a(n) = 1 if n is divisible by at least 2 consecutive primes, 0 otherwise.

0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1

Offset

1

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for characteristic functions

Mathematica

Array[Boole@ MemberQ[Differences@ PrimePi@ FactorInteger[#][[All, 1]], 1] &, 105] (* Michael De Vlieger, Dec 16 2017 *)

Prog

(PARI) A296210(n) = { if(1==n, return(0)); my(ps=factor(n)[, 1], pis=vector(length(ps), i, primepi(ps[i])), diffsminusones = vector(length(pis)-1, i, (pis[i+1]-pis[i])-1)); !factorback(diffsminusones); };

Crossrefs

Cf. A104210, A166469, A192280.

Sequence in context: A133944 A210455 A294936 * A368990 A094912 A103673

Adjacent sequences: A296207 A296208 A296209 * A296211 A296212 A296213

Keyword

nonn

Author

Antti Karttunen, Dec 15 2017

Status

approved