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A293624
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Fermat pseudoprimes to base 2 that are square pyramidal numbers.
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7
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24301222105, 34200607741, 194305088689, 7362505969365, 19702357790989, 2985533798982149, 6091629437910701, 24781034010920641, 98129837465651129, 99860491537987361, 105697961209955269, 154533752639483489, 406611602100644641, 714567498159333701
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OFFSET
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1,1
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COMMENTS
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Rotkiewicz proved that under Schinzel's Hypothesis H this sequence is infinite.
Intersection of A001567 and A000330.
The corresponding indices of A000330 are 4177, 4681, 8353, 28057, 38953, 207673, 263401, 420481, 665233, 669121, 681913, 773953, ...
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LINKS
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Table of n, a(n) for n=1..14.
Andrzej Rotkiewicz, On pyramidal numbers of order 4, Elemente der Mathematik, Vol. 28 (1973), pp. 14-16.
Wikipedia, Schinzel's Hypothesis H.
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MATHEMATICA
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p[n_]:=n(n+1)(2n+1)/6; Select[p[Range[3, 10^6]], PowerMod[2, (#-1), #] == 1 &]
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CROSSREFS
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Cf. A000330, A001567, A293625.
Sequence in context: A015399 A129475 A172612 * A238356 A234064 A017290
Adjacent sequences: A293621 A293622 A293623 * A293625 A293626 A293627
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KEYWORD
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nonn
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AUTHOR
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Amiram Eldar, Oct 13 2017
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STATUS
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approved
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