A030676 Smallest nontrivial extension of n-th palindrome which is a square.

16, 25, 36, 49, 529, 64, 729, 81, 900, 1156, 225, 3364, 441, 55225, 66049, 7744, 8836, 99225, 101124, 111556, 12100, 131044, 14161, 15129, 16129, 17161, 181476, 191844, 2025, 212521, 22201, 232324, 242064, 25281, 26244, 27225

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

revdigs:= proc(n)
local L, nL, i;
L:= convert(n, base, 10);
add(L[-i]*10^(i-1), i=1..nops(L));
end:
g:= proc(d) local m, x, y;
  if d::even then
    m:= d/2;
    seq(x*10^m+revdigs(x), x=10^(m-1)..10^m-1)
  else
    m:= (d-1)/2;
    seq(seq(x*10^(m+1)+y*10^m+revdigs(x), y=0..9), x=10^(m-1)..10^m-1)
  fi
end proc:
g(1):= $1..9:
f:= proc(x) local d, y;
  for d from 1 do
    y:= ceil(sqrt(x*10^d))^2;
    if y < (x+1)*10^d then return y fi
  od;
end proc:
map(f, [g(1), g(2), g(3)]); # Robert Israel, Aug 12 2018

Crossrefs

Cf. A030677.

Sequence in context: A291334 A175689 A030666 * A264604 A348235 A218439

Adjacent sequences: A030673 A030674 A030675 * A030677 A030678 A030679

Keyword

nonn,base,look

Author

Patrick De Geest

Status

approved