cp's OEIS Frontend

A155985 a(1)=1, then a(n) is the smallest square not occurring earlier, not ending with zero and starting with the last digit of a(n-1).

%I A155985 #24 Jul 23 2024 14:44:40
%S A155985 1,16,64,4,49,9,961,121,144,441,169,9025,529,9216,625,576,676,6084,
%T A155985 484,4096,6241,196,6561,1024,4225,5041,1089,9409,9604,4356,6724,4489,
%U A155985 9801,1156,6889,90601,1225,5184,4624,4761,1296,60025,5329,91204,40401,1369
%N A155985 a(1)=1, then a(n) is the smallest square not occurring earlier, not ending with zero and starting with the last digit of a(n-1).
%H A155985 David A. Corneth, <a href="/A155985/b155985.txt">Table of n, a(n) for n = 1..10000</a>
%H A155985 David A. Corneth, <a href="/A155985/a155985_1.gp.txt">PARI program</a>
%o A155985 (PARI) nxt(va, d) = {my(k=1); while ((digits(k^2)[1]!=d) || !(k%10) || #select(x->(x==k^2), va), k++); k^2;}
%o A155985 lista(nn) = {my(va = vector(nn)); va[1] = 1; for (n=2, nn, va[n] = nxt(va, Vecrev(digits(va[n-1]))[1]);); va;} \\ _Michel Marcus_, Sep 04 2020
%o A155985 (PARI) \\ See Corneth link. _David A. Corneth_, Sep 05 2020
%Y A155985 Cf. A076653 (similar, with primes), A155986.
%K A155985 nonn,easy,base
%O A155985 1,2
%A A155985 _Zak Seidov_, Feb 01 2009
%E A155985 Name edited by _Michel Marcus_, Sep 04 2020