

A249896


a(n+1) is next smallest square not divisible by 10 beginning with a(n), initial term is 6.


5



6, 64, 64009, 6400960036, 640096003602877347904, 640096003602877347904912233550482787380625, 6400960036028773479049122335504827873806251020537411455326101704116338781035920283225
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OFFSET

1,1


COMMENTS

a(11) has 1374 digits, a(12) has 2749, a(13) has 5499, a(14) has 10998.  Robert Israel, Nov 25 2020


LINKS

Robert Israel, Table of n, a(n) for n = 1..10
Robert Israel, Table of n, a(n) for n = 1..14


MAPLE

R:= 6: x:= 6: s:= 2:
for iter from 1 while length(x) < 1000 do
for d from 1 do
if d::even then sp:= 1+ 10^(d/2)*s
else
sp:= ceil(sqrt(10^d*x));
if sp mod 10 = 0 then sp:=sp+1; fi
fi;
if sp^2 < (x+1)*10^d then
x:= sp^2; s:= sp; R:= R, x; break
fi
od;
od:
R; # Robert Israel, Nov 25 2020


PROG

(PARI) a(n)=k=n; s=1; while(s<5*10^7, if(s%10, if(s^2\(10^(#Str(s^2)#Str(k)))==k, print1(s^2, ", "); k=s^2)); s++)
a(7)
(Python)
def f(x):
..print(x, end=', ')
..n = x
..s = 1
..while s < 10**7:
....if s % 10:
......S = str(s**2)
......if S.startswith(str(n)):
........print(s**2, end=', ')
........n = s**2
....s += 1
f(7)


CROSSREFS

Cf. A048559, A048561.
Sequence in context: A249592 A333983 A087488 * A249828 A179879 A297516
Adjacent sequences: A249893 A249894 A249895 * A249897 A249898 A249899


KEYWORD

nonn,base,changed


AUTHOR

Derek Orr, Nov 08 2014


STATUS

approved



