1,2

A077655(a(n))=0; A001222(a(n))<>A001222(a(n)+1).

Table of n, a(n) for n=1..71.

20=2*2*5 and 20+1=21=3*7: A001222(20)<>A001222(21), therefore 20 is a term (A077655(20)=0).

Position[Partition[PrimeOmega[Range[100]], 2, 1], _?(#[[1]]!=#[[2]]&), {1}, Heads->False]//Flatten (* Harvey P. Dale, Sep 19 2016 *)

Cf. A001222, A045920.

Sequence in context: A047310 A184530 A304804 * A039236 A304808 A039180

Adjacent sequences: A077653 A077654 A077655 * A077657 A077658 A077659

nonn

Reinhard Zumkeller, Nov 13 2002

approved