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A089619
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Greatest prime factor of n^2 + (n+1)^2.
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0
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5, 13, 5, 41, 61, 17, 113, 29, 181, 17, 53, 313, 73, 421, 37, 109, 613, 137, 761, 29, 37, 1013, 17, 1201, 1301, 281, 89, 13, 1741, 1861, 397, 2113, 449, 2381, 2521, 41, 97, 593, 3121, 193, 53, 3613, 757, 233, 101, 173, 4513, 941, 29, 5101, 1061, 149, 229, 457, 101
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,1
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EXAMPLE
| 2*7^2 - 2*7 + 1 = 85 = 5*17, so a(7)=17.
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PROG
| (PARI) xnpym1n(m) = { for(n=1, m, y = n^2+(n+1)^2; f = factor(y); l = length(component(f, 1)); v = component(component(f, 1), l); print1(v", "); ) }
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CROSSREFS
| Cf. A027861, A027862.
Equals A006530(A001844(n-1)).
Sequence in context: A121645 A057691 A170864 * A094473 A068530 A088315
Adjacent sequences: A089616 A089617 A089618 * A089620 A089621 A089622
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KEYWORD
| easy,nonn
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AUTHOR
| Cino Hilliard (hillcino368(AT)gmail.com), Dec 31 2003
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EXTENSIONS
| Edited by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jan 03 2004
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