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A007961 n written in base where place values are positive squares.

%I A007961 #15 Jul 25 2015 15:52:48
%S A007961 1,2,3,10,11,12,13,20,100,101,102,103,110,111,112,1000,1001,1002,1003,
%T A007961 1010,1011,1012,1013,1020,10000,10001,10002,10003,10010,10011,10012,
%U A007961 10013,10020,10100,10101,100000,100001,100002,100003,100010,100011
%N A007961 n written in base where place values are positive squares.
%C A007961 For n>1: A000196(n) = number of digits of a(n); A190321(n) = number of nonzero digits of a(n); A053610(n) = sum of digits of a(n). [_Reinhard Zumkeller_, May 08 2011]
%H A007961 Reinhard Zumkeller, <a href="/A007961/b007961.txt">Table of n, a(n) for n = 1..10000</a>
%H A007961 F. Smarandache, <a href="http://www.gallup.unm.edu/~smarandache/OPNS.pdf">Only Problems, Not Solutions!</a>.
%p A007961 A007961 := proc(n)
%p A007961     local k,nrem,L,b,d;
%p A007961     k := floor(sqrt(n)) ;
%p A007961     nrem := n ;
%p A007961     L := [] ;
%p A007961     for b from k to 1 by -1 do
%p A007961         d := floor(nrem/b^2) ;
%p A007961         L := [d,op(L)] ;
%p A007961         nrem := nrem -d*b^2 ;
%p A007961     end do:
%p A007961     add( op(i,L)*10^(i-1),i=1..nops(L)) ;
%p A007961 end proc: # _R. J. Mathar_, Jul 25 2015
%o A007961 (Haskell)
%o A007961 import Data.Char (intToDigit)
%o A007961 a007961 :: Integer -> Integer
%o A007961 a007961 n = read $ map intToDigit $
%o A007961   t n $ reverse $ takeWhile (<= n) $ tail a000290_list where
%o A007961     t _ []          = []
%o A007961     t m (x:xs)
%o A007961         | x > m     = 0 : t m xs
%o A007961         | otherwise = (fromInteger m') : t r xs
%o A007961         where (m',r) = divMod m x
%o A007961 -- _Reinhard Zumkeller_, May 08 2011
%Y A007961 Cf. A000290, A000433.
%K A007961 nonn,base
%O A007961 1,2
%A A007961 R. Muller