A008460 Take sum of squares of digits of previous term; start with 6.

6, 36, 45, 41, 17, 50, 25, 29, 85, 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

Offset

1,1

References

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

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..100

Arthur Porges, A set of eight numbers, Amer. Math. Monthly 52 (1945), 379-382.

Index entries for linear recurrences with constant coefficients, signature (0, 0, 0, 0, 0, 0, 0, 1).

Formula

Periodic with period 8.

a(13+n) = A080709(n). - M. F. Hasler, May 24 2009

Mathematica

NestList[Total[IntegerDigits[#]^2]&, 6, 80] (* Vincenzo Librandi, Jan 29 2013 *)

Prog

(PARI) A008460(n)=[6, 36, 45, 41, 17, 50, 25, 29, 85, 89, 145, 42, 20, 4, 16, 37, 58][if(n<18, n, (n-10)%8+10)] \\ M. F. Hasler, May 24 2009
(Magma) [6, 36, 45, 41, 17, 50, 25, 29, 85] cat &cat[[89, 145, 42, 20, 4, 16, 37, 58]: n in [0..17]]; // Vincenzo Librandi, Jan 29 2013

Crossrefs

Cf. A003132 (the iterated map), A003621, A039943, A099645, A031176, A007770, A000216 (starting with 2), A000218 (starting with 3), A080709 (starting with 4), A000221 (starting with 5), A008462 (starting with 8), A008463 (starting with 9), A139566 (starting with 15), A122065 (starting with 74169). - M. F. Hasler, May 24 2009

Sequence in context: A348384 A328466 A232137 * A132633 A372945 A047792

Adjacent sequences: A008457 A008458 A008459 * A008461 A008462 A008463

Keyword

nonn,base,easy

Author

N. J. A. Sloane

Extensions

An erroneous (duplicate) term deleted by M. F. Hasler, May 24 2009

Status

approved