

A272878


a(0) = a(1) = 1, smallest a(n+1) > a(n1) such that a(n)^2 + a(n+1)^2 is prime.


1



1, 1, 2, 3, 8, 5, 16, 9, 26, 11, 30, 13, 32, 15, 34, 21, 44, 29, 46, 39, 50, 43, 60, 61, 64, 71, 66, 79, 74, 81, 100, 83, 102, 95, 104, 101, 114, 109, 134, 115, 136, 135, 146, 139, 154, 141, 160, 143, 168, 155, 172, 165, 178, 173, 190, 177, 200, 189, 206, 199
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OFFSET

0,3


COMMENTS

The associated primes 2, 5, 13, 73, 89, 281, 337, 757, 797, ... create a strictly increasing sequence. What is the rate of its growth?
Positive integers that are not in this sequence are 4, 6, 7, 10, 12, 14, 17, 18, 19, 20, 22, 23, 24, 25, 27, ...  Altug Alkan, May 14 2016


LINKS

Amiram Eldar, Table of n, a(n) for n = 0..10000


MATHEMATICA

a[0]=1; a[1]=1; a[n_]:=a[n]= Block[{t = a[n2] + 1}, While[! PrimeQ[t^2 + a[n1]^2], t++]; t]; Array[a, 80, 0] (* Giovanni Resta, May 08 2016 *)


PROG

(PARI) lista(nn) = {print1(x = 1, ", "); print1(y = 1, ", "); for (n=2, nn, z = x+1; while (! isprime(y^2+z^2), z++); print1(z, ", "); x = y; y = z; ); } \\ Michel Marcus, May 08 2016


CROSSREFS

Cf. A073658, A080478, A100208.
Sequence in context: A097505 A095168 A130479 * A094181 A004730 A332460
Adjacent sequences: A272875 A272876 A272877 * A272879 A272880 A272881


KEYWORD

nonn,look


AUTHOR

Thomas Ordowski, May 08 2016


EXTENSIONS

More terms from Michel Marcus, May 08 2016


STATUS

approved



