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

Author

Derek Orr, Jun 01 2015

Keywords

• nonn
• easy

Comments

1 is the only odd number in this sequence.

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

Crossrefs

Cf. A073659, A073852.

Programs

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

Formula

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