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 A122065 Take sum of squares of digits of previous term; start with 74169. 14
 74169, 183, 74, 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS From a quiz, cf. Russel & Carter reference. REFERENCES K. Russell and P. Carter, Number Puzzles, W. Foulsham and Co. Ltd. (1993). LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..100 Index entries for linear recurrences with constant coefficients, signature (0, 0, 0, 0, 0, 0, 0, 1). FORMULA a(n) = A000218(n) for n >= 4, a(n) = A000216(n-2) for n >= 6. - M. F. Hasler, Apr 27 2018 MATHEMATICA NestList[Total[IntegerDigits[#]^2]&, 74169, 80] (* Vincenzo Librandi, Jan 29 2013 *) PROG (MAGMA) [74169, 183, 74, 65, 61] cat &cat[[37, 58, 89, 145, 42, 20, 4, 16]: n in [0..17]]; // Vincenzo Librandi, Jan 29 2013 (PARI) A122065_vec=vector(50, n, t=if(n>1, norml2(digits(t)), 74169)); A122065(n)=A122065_vec[n%8+(n>7)*8] \\ M. F. Hasler, Apr 27 2018 CROSSREFS Cf. A000216 (main entry for related sequences), A003132 (the iterated "sum digits squared" map). Sequence in context: A256731 A186835 A239587 * A079543 A033450 A033448 Adjacent sequences:  A122062 A122063 A122064 * A122066 A122067 A122068 KEYWORD nonn,base AUTHOR Herman Jamke (hermanjamke(AT)fastmail.fm), Sep 14 2006 STATUS approved

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Last modified April 16 18:53 EDT 2021. Contains 343050 sequences. (Running on oeis4.)