A166376 Triangle in which n-th row (n>1) gives prime factors of n^2 + 1 with repetition.

2, 5, 2, 5, 17, 2, 13, 37, 2, 5, 5, 5, 13, 2, 41, 101, 2, 61, 5, 29, 2, 5, 17, 197, 2, 113, 257, 2, 5, 29, 5, 5, 13, 2, 181, 401, 2, 13, 17, 5, 97, 2, 5, 53, 577, 2, 313, 677, 2, 5, 73, 5, 157, 2, 421, 17, 53, 2, 13, 37, 5, 5, 41

Offset

1,1

Links

Table of n, a(n) for n=1..63.

Example

Since 13^2+1 = 170 = 2*5*17, the three terms 2, 5, 17 appear in the sequence.

Prog

(PARI) row(n)={m=n^2+1; while(m!=1, p=factor(m)[1, 1]; print(p); m=m/p)}

Crossrefs

Cf. A027746 A002522

Sequence in context: A107060 A016589 A151572 * A089122 A321577 A268789

Adjacent sequences: A166373 A166374 A166375 * A166377 A166378 A166379

Keyword

nonn,tabf

Author

Michael B. Porter, Oct 13 2009

Status

approved