A281875 Least k such that phi(k) is the sum of two primes in exactly n ways, or 0 if no such k exists.
1, 5, 11, 23, 37, 65, 61, 79, 103, 161, 127, 157, 143, 199, 181, 307, 277, 313, 241, 211, 409, 341, 379, 487, 331, 623, 577, 551, 463, 527, 421, 571, 601, 673, 829, 757, 877, 997, 1571, 691, 1039, 631, 1009, 961, 869, 967, 1543, 989, 1057, 1247, 2411, 899, 991, 1303, 1147, 1231, 1999
Offset: 0
Examples
a(3) = 23 because phi(23) = 22 = 3 + 19 = 5 + 17 = 11 + 11 and 23 is the least number with this property.
Links
- Chai Wah Wu, Table of n, a(n) for n = 0..10000
Extensions
a(0) = 1 prepended by Chai Wah Wu, Feb 03 2017
Comments