This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A385054 #7 Jun 17 2025 08:13:03 %S A385054 60,140,196,280,295,332,390,468,574,581,604,605,621,740,760,826,876, %T A385054 935,1012,1070,1148,1183,1185,1210,1225,1240,1269,1278,1284,1376,1420, %U A385054 1484,1526,1535,1556,1690,1692,1715,1828,1906,1908,1910,1914,1928,1935,1964,2000 %N A385054 Numbers k such that (2*k-1)*2^valuation(k, 2) != denominator(2*Euler(2*k-1, 1)/(2*k-1)). %p A385054 a := n -> ifelse((2*n-1)*2^ordp(n,2) = denom(2*euler(2*n-1,1)/(2*n-1)), NULL, n): %p A385054 seq(a(n), n = 1..1000); %t A385054 Select[Range[1000], Denominator[2*EulerE[2*# - 1, 1]/(2*# - 1)] != (2*# - 1)*2^IntegerExponent[#, 2] &] (* _Amiram Eldar_, Jun 16 2025 *) %Y A385054 Cf. A219931. %K A385054 nonn %O A385054 1,1 %A A385054 _Peter Luschny_, Jun 16 2025