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

1,2

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.

Links

Table of n, a(n) for n=1..70.

Prog

(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)<n);

Crossrefs

Positions of strictly positive terms in A364288.

Subsequence of A364291.

Cf. A243071, A364289 (complement).

Cf. also A364287.

Sequence in context: A347202 A036349 A352827 * A155562 A048715 A336232

Adjacent sequences: A364287 A364288 A364289 * A364291 A364292 A364293

Keyword

nonn

Author

Antti Karttunen, Jul 25 2023

Status

approved