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Search: id:A058854
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| A058854 |
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a(n) = largest prime in the factorization of (n+1)-st Franel number (A000172). |
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+0
1
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| 2, 5, 7, 173, 563, 73, 41, 369581, 1409, 109, 449, 176459, 44221, 12148537, 148381, 11399977, 5779337237, 16111, 26013917, 57405011, 3019, 1973, 191141, 6730949, 998917, 6619, 3853, 5153, 138961158000728258971, 2593, 6511107455627473
(list; graph; listen)
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OFFSET
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0,1
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EXAMPLE
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a(3)=173 because the 4-th Franel number is 346 = 2^1 * 173^1, in which 173 is the largest prime.
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MAPLE
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with(combinat): with(numtheory): A000172 := n->sum(binomial(n, k)^3, k=0..n): for n from 1 to 50 do printf(`%d, `, ifactors(A000172(n))[2][nops(ifactors(A000172(n))[2])][1]) od:
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MATHEMATICA
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Do[ Print[ FactorInteger[ Sum[ Binomial[n, k]^3, {k, 0, n}]] [[ -1, 1]] ], {n, 1, 32} ]
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CROSSREFS
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Cf. A000172.
Sequence in context: A103056 A041445 A041961 this_sequence A006275 A042673 A007571
Adjacent sequences: A058851 A058852 A058853 this_sequence A058855 A058856 A058857
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KEYWORD
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nonn
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AUTHOR
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Felix Goldberg (felixg(AT)tx.technion.ac.il), Jan 30 2001
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EXTENSIONS
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More terms from James A. Sellers (sellersj(AT)math.psu.edu), Feb 01 2001
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