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A035497
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Happy primes: primes that eventually reach 1 under iteration of "x -> sum of squares of digits of x".
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8
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7, 13, 19, 23, 31, 79, 97, 103, 109, 139, 167, 193, 239, 263, 293, 313, 331, 367, 379, 383, 397, 409, 487, 563, 617, 653, 673, 683, 709, 739, 761, 863, 881, 907, 937, 1009, 1033, 1039, 1093, 1151, 1277, 1303, 1373, 1427, 1447, 1481, 1487, 1511, 1607, 1663
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listen;
history;
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internal format)
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OFFSET
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1,1
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COMMENTS
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The 2nd and 3rd repunit primes, 1111111111111111111 and 11111111111111111111111 are happy primes. - Thomas M. Green (tgreen(AT)astound.net), Oct 23 2009
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REFERENCES
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R. K. Guy, Unsolved Problems Number Theory, Sect. E34.
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LINKS
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Nathaniel Johnston, Table of n, a(n) for n = 1..10000
C. Rivera, Related puzzle page
Eric Weisstein's World of Mathematics, Happy Number
Wikipedia, Happy number
Doctor Who, Episode 42
Wikipedia, Doctor Who, Episode 42
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MATHEMATICA
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g[n_] := Total[ IntegerDigits[n]^2]; fQ[n_] := NestWhileList[g@# &, n, UnsameQ, All][[-1]] == 1; Select[Prime@ Range@ 300, fQ@# &] (* Robert G. Wilson v, Jan 03 2013 *)
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CROSSREFS
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Cf. A007770 (happy numbers), A046519.
Sequence in context: A209623 A058620 A038910 * A216527 A059335 A070419
Adjacent sequences: A035494 A035495 A035496 * A035498 A035499 A035500
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KEYWORD
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nonn,easy,base
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AUTHOR
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N. J. A. Sloane.
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EXTENSIONS
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More terms from Patrick De Geest, Oct 15 1999.
Doctor Who links from David Applegate, Oct 06 2008
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STATUS
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approved
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