%I #31 Oct 21 2022 22:07:45
%S 6,36,45,41,17,50,25,29,85,89,145,42,20,4,16,37,58,89,145,42,20,4,16,
%T 37,58,89,145,42,20,4,16,37,58,89,145,42,20,4,16,37,58,89,145,42,20,4,
%U 16,37,58,89,145,42,20,4,16,37,58,89,145,42,20,4,16,37,58,89,145,42,20,4
%N Take sum of squares of digits of previous term; start with 6.
%D R. Honsberger, Ingenuity in Mathematics, Random House, 1970, p. 83.
%H Vincenzo Librandi, <a href="/A008460/b008460.txt">Table of n, a(n) for n = 1..100</a>
%H Arthur Porges, <a href="http://www.jstor.org/stable/2304639">A set of eight numbers</a>, Amer. Math. Monthly 52 (1945), 379-382.
%H <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 0, 0, 0, 0, 1).
%F Periodic with period 8.
%F a(13+n) = A080709(n). - _M. F. Hasler_, May 24 2009
%t NestList[Total[IntegerDigits[#]^2]&, 6, 80] (* _Vincenzo Librandi_, Jan 29 2013 *)
%o (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
%o (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
%Y 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
%K nonn,base,easy
%O 1,1
%A _N. J. A. Sloane_
%E An erroneous (duplicate) term deleted by _M. F. Hasler_, May 24 2009