A292379 Odd numbers k such that A292270((k-1)/2) is a square < ((k-1)/2)^2.

7, 15, 27, 31, 63, 95, 127, 255, 277, 305, 511, 519, 1023, 1921, 2047, 2349, 3575, 4095, 8191, 8743, 10525, 16383, 17955, 24661, 26585, 27305, 32767, 36611, 40677, 65535, 85173, 95571, 122915, 131071, 262143, 360213, 386019, 524287, 667879, 736251, 806603, 1020963

Offset: 1

Author

Antti Karttunen and Vladimir Shevelev, Oct 06 2017

Keywords

• nonn

Crossrefs

Subsequence of A292939.

Doesn't contain any terms of A001122.

Cf. A000225 (subsequence from its term a(3) = 7 onward).

Cf. A292270.

Programs

PARI

A000265(n) = n >> valuation(n, 2);
A292270(n) = { my(x = n+n+1, m = A000265(1+x), z = m); while(m!=1, z += A000265(x+m); m = A000265(x+m)); z; };
n=1; k=0; while(k < 120, m = A292270(n); if(issquare(m) && (m < n^2), k++; write("b292379.txt", k, " ", 1+(2*n))); n++);

Extensions

More terms from Jinyuan Wang, Apr 29 2025