A249064 Lexically first sequence of distinct positive integers such that a(n) is coprime to the next a(n) elements.

1, 2, 3, 5, 4, 7, 9, 11, 13, 8, 17, 19, 23, 25, 29, 31, 21, 37, 16, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 22, 109, 113, 27, 35, 127, 131, 137, 139, 149, 151, 157, 163, 167, 169, 173, 179, 181, 191, 193, 197, 199, 211, 32, 121, 223, 227, 229, 233, 239, 241, 51, 251, 257, 263, 269, 271, 277, 281, 283, 49, 95

Offset

1,2

Comments

Described in this form, A090252 would be "lexically first sequence of positive integers such that a(n) is coprime to the next n elements".

(And A247665 would be "lexically first sequence of integers >= 2 such that a(n) is coprime to the next n elements". - N. J. A. Sloane, Nov 01 2014)

All values up to a(1000000) are either prime powers or semiprimes, except when n is in (868, 947, 993, 1069, 1205, 1431, 854300) with values respectively (172, 45, 75, 135, 225, 375, 9475). This suggests the sequence is unlikely to be a permutation of the integers.

If, mimicking A247665, one starts with a(1)=2 and uses the same rule (always using distinct numbers >= 2) one obtains A249064 again, without the leading 1. - N. J. A. Sloane, Nov 01 2014

Links

Hugo van der Sanden, Table of n, a(n) for n = 1..1001

Hugo van der Sanden, Perl program to calculate this sequence and A090252 (requires Math::Pari)

Hugo van der Sanden, Faster Perl program on github.

Crossrefs

Cf. A090252, A247665, A249557.

Sequence in context: A269367 A322863 A081994 * A257489 A090252 A140140

Adjacent sequences: A249061 A249062 A249063 * A249065 A249066 A249067

Keyword

nonn

Author

Hugo van der Sanden, Oct 20 2014

Extensions

Added "distinct" to the definition. - Hugo van der Sanden, Oct 28 2014

Status

approved