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 A381702 #15 Mar 15 2025 16:31:41 %S A381702 2,6,11,14,19,22,53,31,137,38,43,46,101,81,59,62,67,71,149,79,83,86, %T A381702 181,94,197,103,107,121,229,118,977,127,131,134,139,142,293,151,617, %U A381702 158,163,166,1361,258,179,362,373,191,389,199,809,206,211,214,6977,223,227,458,937,239,30977,1954,251,254,1033,262 %N A381702 a(n) is the least k such that A277847(k) = 2*n. %e A381702 Table of n, a(n), A277847(a(n)), [row(a(n))] starts (where row(n) is row n of A381348): %e A381702 1, 2, 2, [0,1] %e A381702 2, 6, 4, [0,1,3,4] %e A381702 3, 11, 6, [0,1,3,4,5,9] %e A381702 4, 14, 8, [0,1,2,4,7,8,9,11] %e A381702 5, 19, 10, [0,1,4,5,6,7,9,11,16,17] %e A381702 6, 22, 12, [0,1,3,4,5,9,11,12,14,15,16,20] %e A381702 ... %o A381702 (Python) %o A381702 from math import prod %o A381702 from sympy import totient, factorint %o A381702 def A277847(n): return prod(((m:=int(totient(p**e)))>>(~m&m-1).bit_length())+1 for p, e in factorint(n).items()) %o A381702 def a(n): %o A381702 n,i = 2*n,1 %o A381702 while True: %o A381702 if A277847(i) == n: return i; i += 1 %Y A381702 Cf. A381348, A277847. %K A381702 nonn %O A381702 1,1 %A A381702 _Aloe Poliszuk_, Mar 03 2025