A364290 Numbers k such that A243071(k) < k.

1, 2, 4, 8, 9, 15, 16, 18, 25, 27, 30, 32, 35, 36, 45, 49, 50, 54, 60, 63, 64, 70, 72, 75, 77, 81, 90, 98, 100, 105, 108, 120, 121, 125, 126, 128, 135, 140, 143, 144, 147, 150, 154, 162, 165, 169, 175, 180, 189, 196, 200, 210, 216, 225, 231, 240, 242, 243, 245, 250, 252, 256, 270, 273, 275, 280, 286, 288, 289, 294

Offset: 1

Author

Antti Karttunen, Jul 25 2023

Keywords

• nonn

Comments

If k is present, then 2*k is also present, and vice versa.

361 = 19^2 is the first square that is not present in this sequence.

Crossrefs

Positions of strictly positive terms in A364288.

Subsequence of A364291.

Cf. A243071, A364289 (complement).

Cf. also A364287.

Programs

PARI

A064989(n) = { my(f=factor(n>>valuation(n,2))); for(i=1, #f~, f[i,1] = precprime(f[i,1]-1)); factorback(f); };
A243071(n) = if(n<=2, n-1, if(!(n%2), 2*A243071(n/2), 1+(2*A243071(A064989(n)))));
isA364290(n) = (A243071(n)