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Subsequence of the automorphic numbers (A003226) with initial term 5 and such that a(n+1) ends with the digits of a(n).
2

%I #20 Jun 27 2016 03:57:42

%S 5,25,625,12890625,6259918212890625,4106619977392256259918212890625,

%T 80863811000557423423230896109004106619977392256259918212890625

%N Subsequence of the automorphic numbers (A003226) with initial term 5 and such that a(n+1) ends with the digits of a(n).

%C An automorphic number is a number whose square ends in the same digits as the number itself.

%C The next term has 126 digits.

%H Colin Barker, <a href="/A274463/b274463.txt">Table of n, a(n) for n = 1..10</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Automorphic_number">Automorphic number</a>

%o (PARI)

%o seq(m, maxn) = L=List(); for(j=1, maxn, listput(L, m); m=(3*m^2-2*m^3)%10 ^ (2*sizedigit(m))); Vec(L)

%o seq(5, 8)

%Y Cf. A003226, A274464.

%K nonn,base

%O 1,1

%A _Colin Barker_, Jun 24 2016