cp's OEIS Frontend

A019521 Concatenate squares.

%I A019521 #53 Feb 16 2025 08:32:33
%S A019521 1,14,149,14916,1491625,149162536,14916253649,1491625364964,
%T A019521 149162536496481,149162536496481100,149162536496481100121,
%U A019521 149162536496481100121144,149162536496481100121144169,149162536496481100121144169196,149162536496481100121144169196225
%N A019521 Concatenate squares.
%C A019521 a(3)=149 is the only prime up to n=4000. - _Daniel Arribas_, Jun 04 2016
%D A019521 S. Smarandoiu, Convergence of Smarandache continued fractions, Abstract 96T-11-195, Abstracts Amer. Math. Soc., Vol. 17, No. 4 (1996), p. 680.
%H A019521 Reinhard Zumkeller, <a href="/A019521/b019521.txt">Table of n, a(n) for n = 1..225</a>
%H A019521 Y. Guo and M. Le, <a href="http://vixra.org/abs/1403.0549">Smarandache Concatenated Power Decimals and Their Irrationality</a>, Smarandache Notions Journal, Vol. 9, No. 1-2 (1998), pp. 100-102.
%H A019521 F. Smarandache, <a href="http://www.gallup.unm.edu/~smarandache/CP2.pdf">Collected Papers, Vol. II</a>.
%H A019521 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ConsecutiveNumberSequences.html">Consecutive Number Sequences</a>.
%p A019521 a:= proc(n) a(n):= `if`(n=1, 1, parse(cat(a(n-1), n^2))) end:
%p A019521 seq(a(n), n=1..20);  # _Alois P. Heinz_, Jan 13 2021
%o A019521 (Haskell)
%o A019521 a019521 n = a019521_list !! (n-1)
%o A019521 a019521_list = f "" $ tail a000290_list where
%o A019521    f xs (q:qs) = (read ys :: Integer) : f ys qs
%o A019521      where ys = xs ++ show q
%o A019521 -- _Reinhard Zumkeller_, Mar 01 2014
%o A019521 (Python)
%o A019521 def a(n): return int("".join(str(i*i) for i in range(1, n+1)))
%o A019521 print([a(n) for n in range(1, 16)]) # _Michael S. Branicky_, Jan 14 2021
%Y A019521 Cf. A000290, A007908, A038397.
%K A019521 base,nonn
%O A019521 1,2
%A A019521 R. Muller