A256270 a(1) = 1; for n > 1, a(n) is the smallest positive integer not already in the sequence such that a(1)^2 + a(2)^2 + ... + a(n)^2 is prime.

1, 2, 6, 24, 12, 54, 18, 36, 30, 48, 60, 84, 42, 90, 66, 72, 96, 78, 120, 126, 102, 150, 144, 108, 156, 114, 138, 132, 180, 204, 210, 168, 186, 192, 234, 174, 162, 216, 198, 222, 246, 228, 264, 348, 240, 270, 300, 330, 336, 402, 390, 414, 288, 306, 258, 294, 318, 324, 276, 252, 372, 426, 366, 282, 432, 354, 378

Offset

1,2

Comments

1 is the only odd number in this sequence.

Excluding 1 and 2, this is a permutation of the positive multiples of 6.

Links

Table of n, a(n) for n=1..67.

Formula

a(n)^2 = A073852(n).

Prog

(PARI) v=[1]; n=1; while(n<10^3, if(isprime(n^2+sum(i=1, #v, v[i]^2))&&!vecsearch(vecsort(v), n), v=concat(v, n); n=1); n++); v

Crossrefs

Cf. A073659, A073852.

Sequence in context: A370252 A181952 A345902 * A243657 A321475 A356757

Adjacent sequences: A256267 A256268 A256269 * A256271 A256272 A256273

Keyword

nonn,easy

Author

Derek Orr, Jun 01 2015

Status

approved