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Search: id:A101746
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| A101746 |
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Primes of the form ((0!)^2+(1!)^2+(2!)^2+...+(n!)^2)/6. |
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+0
2
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| 7, 103, 2503, 88903, 4322503, 2473107965928318342544472044975303
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Let S(n)=sum_{i=0,..n-1} (i!)^2. Note that 6 divides S(n) for n>1. For prime p=20879, p divides S(p-1). Hence p divides S(n) for all n >= p-1 and all prime values of S(n)/6 are for n < p-1.
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MATHEMATICA
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f2=1; s=2; Do[f2=f2*n*n; s=s+f2; If[PrimeQ[s/6], Print[{n, s/6}]], {n, 2, 100}]
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CROSSREFS
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Cf. A061062 (S(n)), A100288 (primes of the form S(n)-1), A100289 (n such that S(n)-1 is prime), A101747 (n such that S(n)/6 is prime).
Sequence in context: A140633 A142400 A032460 this_sequence A001921 A098362 A093741
Adjacent sequences: A101743 A101744 A101745 this_sequence A101747 A101748 A101749
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KEYWORD
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fini,nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Dec 18 2004
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