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A166376
Triangle in which n-th row (n>1) gives prime factors of n^2 + 1 with repetition.
0
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
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
KEYWORD
nonn,tabf
AUTHOR
Michael B. Porter, Oct 13 2009
STATUS
approved