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A072494
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First of triples of consecutive happy numbers, i.e. the first of three consecutive integers each of which is a happy number (A007770).
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3
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1880, 4780, 4870, 7480, 7839, 7840, 8180, 8470, 8739, 8740, 8810, 10880, 11248, 11249, 11519, 12148, 12149, 13898, 15119, 18080, 18800, 21148, 21149, 23308, 25680, 25860, 26580, 26850, 28560, 28650, 31898, 32308, 33208, 33319, 40780, 40870, 44488, 44489
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| David Wells, The Penguin Dictionary of Curious and Interesting Numbers, p. 154 (Rev. ed. 1997).
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LINKS
| Eric Weisstein's World of Mathematics, Happy Number
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EXAMPLE
| 7480 is included because 7480, 7481 and 7482 are all happy numbers.
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MATHEMATICA
| happyQ[n_] := Nest[Plus @@(IntegerDigits[ # ]^2\)&, n, 50] == 1); Transpose[Select[Partition[Select[Range[50000], happyQ], 3, 1], #[[3]] - #[[2]] == #[[2]] - #[[1]] == 1 &]][[1]]
f[n_] := Total[IntegerDigits[n]^2]; t = Select[Range[50000], NestWhile[f, #, UnsameQ, All] == 1 &]; t[[Select[Range[Length[t] - 2], t[[#]] == t[[# + 1]] - 1 == t[[# + 2]] - 2 &]]] (* T. D. Noe, Aug 23 2011 *)
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CROSSREFS
| Sequence in context: A127410 A045201 A020407 * A190133 A029564 A206746
Adjacent sequences: A072491 A072492 A072493 * A072495 A072496 A072497
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KEYWORD
| nonn,base
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AUTHOR
| Harvey P. Dale (hpd1(AT)nyu.edu), Aug 02 2002
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