A381702 a(n) is the least k such that A277847(k) = 2*n.

2, 6, 11, 14, 19, 22, 53, 31, 137, 38, 43, 46, 101, 81, 59, 62, 67, 71, 149, 79, 83, 86, 181, 94, 197, 103, 107, 121, 229, 118, 977, 127, 131, 134, 139, 142, 293, 151, 617, 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

Offset: 1

Author

Aloe Poliszuk, Mar 03 2025

Keywords

• nonn

Examples

			Table of n, a(n), A277847(a(n)), [row(a(n))] starts (where row(n) is row n of A381348):
  1, 2,  2,  [0,1]
  2, 6,  4,  [0,1,3,4]
  3, 11, 6,  [0,1,3,4,5,9]
  4, 14, 8,  [0,1,2,4,7,8,9,11]
  5, 19, 10, [0,1,4,5,6,7,9,11,16,17]
  6, 22, 12, [0,1,3,4,5,9,11,12,14,15,16,20]
  ...
		

Crossrefs

Cf. A381348, A277847.

Programs

Python

from math import prod
from sympy import totient, factorint
def A277847(n): return prod(((m:=int(totient(p**e)))>>(~m&m-1).bit_length())+1 for p, e in factorint(n).items())
def a(n):
    n,i = 2*n,1
    while True:
        if A277847(i) == n: return i; i += 1