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A072494 First of triples of consecutive happy numbers, i.e. the first of three consecutive integers each of which is a happy number (A007770). 3
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; text; internal format)
OFFSET

1,1

REFERENCES

David Wells, The Penguin Dictionary of Curious and Interesting Numbers, p. 154 (Rev. ed. 1997).

LINKS

Table of n, a(n) for n=1..38.

Eric Weisstein's World of Mathematics, Happy Number

EXAMPLE

7480 is included because 7480, 7481 and 7482 are all happy numbers.

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 *)

CROSSREFS

Sequence in context: A045201 A020407 A235193 * A237103 A222799 A236613

Adjacent sequences:  A072491 A072492 A072493 * A072495 A072496 A072497

KEYWORD

nonn,base

AUTHOR

Harvey P. Dale, Aug 02 2002

STATUS

approved

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Last modified April 17 14:52 EDT 2014. Contains 240645 sequences.