

A000216


Take sum of squares of digits of previous term, starting with 2.


20



2, 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, 58, 89, 145, 42, 20, 4, 16, 37
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OFFSET

1,1


COMMENTS

As the orbit of 2 under A003132, this could also have offset 0. Merges into A080709 right after the first term: a(n+1) = A080709(n) for all n >= 1.  M. F. Hasler, Apr 27 2018


REFERENCES

R. Honsberger, Ingenuity in Mathematics, Random House, 1970, p. 83.
P. Kiss, A generalization of a problem in number theory, Math. Sem. Notes Kobe Univ., 5 (1977), no. 3, 313317. MR 0472667 (57 #12362).


LINKS



FORMULA

Periodic with period 8.


MATHEMATICA



PROG

(PARI) A000216(n)=[42, 20, 4, 16, 37, 58, 89, 145, 2][n%8+8^(n<2)] \\ M. F. Hasler, May 24 2009, edited Apr 27 2018
(Haskell) a000216 n = a000216_list !! (n1)
(Magma) [2] cat &cat[[4, 16, 37, 58, 89, 145, 42, 20]: n in [0..17]]; // Vincenzo Librandi, Jan 29 2013


CROSSREFS

Cf. A003132 (the iterated map), A003621, A039943, A099645, A031176, A007770, A000218 (starting with 3), 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



