login
A180405
Smallest integer not yet present in the sequence such that the sum of the first a(n) terms of the sequence is a prime.
4
2, 1, 4, 6, 3, 7, 8, 10, 11, 15, 12, 18, 14, 16, 22, 24, 19, 31, 28, 20, 23, 37, 36, 30, 26, 34, 29, 35, 42, 38, 40, 32, 39, 45, 52, 44, 54, 46, 56, 60, 43, 51, 50, 64, 84, 48, 49, 53, 68, 58, 62, 78, 70, 66, 57, 59, 82, 92, 90, 88, 63, 77, 72, 94, 67, 79, 76, 102, 71, 81, 96, 100
OFFSET
1,1
COMMENTS
From an idea of Eric Angelini with additional terms from D. S. McNeil.
The partial sums of the sequence are 2, 3, 7, 13, 16, 23, 31, 41, 52, ...
The sequence is self-descriptive and says that the 2nd, 1st, 4th, 6th, 3rd, 7th, etc, term in the partial sums, namely 3, 2, 13, 23, 7, 31 etc, are primes.
LINKS
Eric Angelini, The sum of the a(n) first digits of S is a prime [Cached copy, with permission]
CROSSREFS
Cf. A054408, A171007 (digits version), A363379 (complement).
Sequence in context: A306015 A171087 A105364 * A171007 A209168 A209162
KEYWORD
easy,nonn
AUTHOR
Paolo P. Lava, Sep 02 2010
EXTENSIONS
Examples replaced with a comment by R. J. Mathar, Nov 18 2010
STATUS
approved