A385054 Numbers k such that (2*k-1)*2^valuation(k, 2) != denominator(2*Euler(2*k-1, 1)/(2*k-1)).

60, 140, 196, 280, 295, 332, 390, 468, 574, 581, 604, 605, 621, 740, 760, 826, 876, 935, 1012, 1070, 1148, 1183, 1185, 1210, 1225, 1240, 1269, 1278, 1284, 1376, 1420, 1484, 1526, 1535, 1556, 1690, 1692, 1715, 1828, 1906, 1908, 1910, 1914, 1928, 1935, 1964, 2000

Offset: 1

Author

Peter Luschny, Jun 16 2025

Keywords

• nonn

Crossrefs

Cf. A219931.

Programs

Maple

a := n -> ifelse((2*n-1)*2^ordp(n,2) = denom(2*euler(2*n-1,1)/(2*n-1)), NULL, n):
seq(a(n), n = 1..1000);

Mathematica

Select[Range[1000], Denominator[2*EulerE[2*# - 1, 1]/(2*# - 1)] != (2*# - 1)*2^IntegerExponent[#, 2] &] (* Amiram Eldar, Jun 16 2025 *)