Search: id:A000218
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%I A000218
%S A000218 3,9,81,65,61,37,58,89,145,42,20,4,16,37,58,89,145,42,20,
%T A000218 4,16,37,58,89,145,42,20,4,16,37,58,89,145,42,20,4,16,37,
%U A000218 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
%N A000218 Take sum of squares of digits of previous term.
%D A000218 R. Honsberger, Ingenuity in Math., Random House, 1970, p. 83.
%D A000218 A. Porges, A set of eight numbers, Amer. Math. Monthly, 52 (1945), 379-382.
%F A000218 Periodic with period 8.
%o A000218 (PARI) A000218(n)=[3, 9, 81, 65, 61, 37, 58, 89, 145, 42, 20, 4, 16][n%8+(n%8<6 
               & n>7)*8] \\\\ [From M. F. Hasler (MHasler(AT)univ-ag.fr), May 24 
               2009]
%Y A000218 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). [From M. F. Hasler (MHasler(AT)univ-ag.fr), May 24 2009]
%Y A000218 Sequence in context: A132294 A032330 A018604 this_sequence A139731 A124049 
               A067623
%Y A000218 Adjacent sequences: A000215 A000216 A000217 this_sequence A000219 A000220 
               A000221
%K A000218 nonn,base
%O A000218 1,1
%A A000218 N. J. A. Sloane (njas(AT)research.att.com).

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