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

0,2

Comments

Note that this sequence is not the subsequence of A037143; i.e., a(318) = 7^3 * 47.

Links

Chai Wah Wu, Table of n, a(n) for n = 0..10000

Example

a(3) = 23 because phi(23) = 22 = 3 + 19 = 5 + 17 = 11 + 11 and 23 is the least number with this property.

Crossrefs

Cf. A000010, A001172, A023036, A281816.

Sequence in context: A061769 A169744 A190148 * A143125 A147081 A046628

Adjacent sequences: A281872 A281873 A281874 * A281876 A281877 A281878

Keyword

nonn,look

Author

Altug Alkan, Feb 01 2017

Extensions

a(0) = 1 prepended by Chai Wah Wu, Feb 03 2017

Status

approved