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A241081 Numbers that are not perfect squares but that can never be ruled out as perfect squares by any final group of digits. 2
41, 89, 129, 161, 164, 201, 209, 241, 249, 281, 321, 329, 356, 369, 401, 409, 449, 481, 489, 516, 521, 561, 569, 601, 609, 641, 644, 649, 656, 681, 689, 721, 761, 769, 801, 804, 809, 836, 849, 881, 889, 921, 929, 964, 969, 996, 1001, 1009, 1025, 1041 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All nonsquare numbers of the form 40n+1 or 40n+9 multiplied by a power of 4 times a power of 25.

LINKS

Table of n, a(n) for n=1..50.

EXAMPLE

41 is in the sequence because there are square numbers ending in ...00041 for any number of zeros.

49 isn't in the sequence because it is a perfect square.

50 isn't in the sequence because there are no squares ending in 50.

PROG

(PARI) al(n) = {local(r=vector(n), x41, x49, i4=1, x4, i25=1, x25);

   x41=41; x49=89; x4=4*41; x25=25*41;

   for(k=1, n, r[k]=min(min(x41, x49), min(x4, x25));

      if(r[k]==x41, while(issquare(x41+=40), 0));

      if(r[k]==x49, while(issquare(x49+=40), 0));

      if(r[k]==x4, x4=4*r[i4++]);

      if(r[k]==x25, x25=25*r[i25++]));

r} \\ Franklin T. Adams-Watters, Apr 18 2014

CROSSREFS

Sequence in context: A242708 A282533 A199983 * A188173 A142411 A139924

Adjacent sequences:  A241078 A241079 A241080 * A241082 A241083 A241084

KEYWORD

nonn,base

AUTHOR

J. Lowell, Apr 15 2014

EXTENSIONS

More terms from Franklin T. Adams-Watters, Apr 18 2014

STATUS

approved

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Last modified August 7 19:55 EDT 2022. Contains 355994 sequences. (Running on oeis4.)