

A163522


a(1)=2; for n>1, a(n) = sum of digits of a(n1)^2.


2



2, 4, 7, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16, 13, 16
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


LINKS

Antti Karttunen, Table of n, a(n) for n = 1..1001
Index entries for linear recurrences with constant coefficients, signature (0,1).


FORMULA

G.f.: x*(2 + 4*x + 5*x^2 + 9*x^3 + 9*x^4)/((1  x)*(1 + x)).  Bruno Berselli, May 29 2014


EXAMPLE

a(2)=4 because 2^2=4;
a(3)=7 because 4^2=16 and 6+1=7;
a(4)=13 because 7^2=49 and 4+9=13.
Other similar sequences, starting from 3, 5, 7 respectively:
. 3, 9 (9 repeated);
. 5, 7, 13, 16, 13 (13, 16 repeated);
. 8, 10, 1 (1 repeated).


MATHEMATICA

Join[{2, 4, 7}, LinearRecurrence[{0, 1}, {13, 16}, 50]] (* or *) CoefficientList[Series[x*(2 + 4*x + 5*x^2 + 9*x^3 + 9*x^4)/((1  x)*(1 + x)), {x, 0, 50}], x] (* G. C. Greubel, Jul 27 2017 *)
PadRight[{2, 4, 7}, 120, {16, 13}] (* Harvey P. Dale, Aug 29 2021 *)


PROG

(PARI) x='x+O('x^50); Vec(x*(2 + 4*x + 5*x^2 + 9*x^3 + 9*x^4)/((1  x)*(1 + x))) \\ G. C. Greubel, Jul 27 2017
(Scheme) (define (A163522 n) (cond ((<= n 2) (expt 2 n)) ((= 3 n) 7) ((even? n) 13) (else 16))) ;; Antti Karttunen, Sep 14 2017


CROSSREFS

Cf. A007953.
Sequence in context: A177101 A018414 A002152 * A255173 A002466 A162842
Adjacent sequences: A163519 A163520 A163521 * A163523 A163524 A163525


KEYWORD

nonn,base,easy


AUTHOR

Vincenzo Librandi, Jul 30 2009


EXTENSIONS

Edited by N. J. A. Sloane, Aug 01 2009
Edited by Bruno Berselli, May 29 2014


STATUS

approved



