This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A122065 #21 Oct 21 2022 22:02:05 %S A122065 74169,183,74,65,61,37,58,89,145,42,20,4,16,37,58,89,145,42,20,4,16, %T A122065 37,58,89,145,42,20,4,16,37,58,89,145,42,20,4,16,37,58,89,145,42,20,4, %U A122065 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 A122065 Take sum of squares of digits of previous term; start with 74169. %C A122065 From a quiz, cf. Russel & Carter reference. %D A122065 K. Russell and P. Carter, Number Puzzles, W. Foulsham and Co. Ltd. (1993). %H A122065 Vincenzo Librandi, <a href="/A122065/b122065.txt">Table of n, a(n) for n = 1..100</a> %H A122065 <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 A122065 a(n) = A000218(n) for n >= 4, a(n) = A000216(n-2) for n >= 6. - _M. F. Hasler_, Apr 27 2018 %t A122065 NestList[Total[IntegerDigits[#]^2]&, 74169, 80] (* _Vincenzo Librandi_, Jan 29 2013 *) %o A122065 (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 %o A122065 (PARI) A122065_vec=vector(50,n,t=if(n>1,norml2(digits(t)),74169)); %o A122065 A122065(n)=A122065_vec[n%8+(n>7)*8] \\ _M. F. Hasler_, Apr 27 2018 %Y A122065 Cf. A000216 (main entry for related sequences), A003132 (the iterated "sum digits squared" map). %K A122065 nonn,base,easy %O A122065 1,1 %A A122065 Herman Jamke (hermanjamke(AT)fastmail.fm), Sep 14 2006