

A000218


Take sum of squares of digits of previous term; start with 3.


16



3, 9, 81, 65, 61, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37, 58, 89, 145, 42, 20, 4, 16, 37
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OFFSET

1,1


COMMENTS

Could also have offset 0, considered as the orbit of 3 under A003132, i.e., nfold application of A003132 on the initial value 3.  M. F. Hasler, Apr 27 2018


REFERENCES

R. Honsberger, Ingenuity in Math., Random House, 1970, p. 83.


LINKS



FORMULA

Eventually periodic with period 8.


MATHEMATICA



PROG

(PARI) A000218(n)=[89, 145, 42, 20, 4, 16, 37, 58, 3, 9, 81, 65, 61][n%8+8^(n<6)] \\ M. F. Hasler, May 24 2009, edited Apr 27 2018
(Haskell)
a000218 n = a000218_list !! (n1)
a000218_list = iterate a003132 3
(Magma) [3, 9, 81, 65, 61] cat &cat[[37, 58, 89, 145, 42, 20, 4, 16]: n in [0..17]]; // Vincenzo Librandi, Jan 29 2013


CROSSREFS

Cf. A003132 (the iterated map), A003621, A039943, A099645, A031176, A007770, A000216 (starting with 2), A080709 (starting with 4), A000221 (starting with 5), A008460 (starting with 6), A008462 (starting with 8), A008463 (starting with 9), A139566 (starting with 15), A122065 (starting with 74169).  M. F. Hasler, May 24 2009


KEYWORD

nonn,base,easy


AUTHOR



STATUS

approved



