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A249893 a(n+1) is next smallest square not divisible by 10 beginning with a(n), initial term is 2. 4
2, 25, 256, 256036, 2560361612769, 256036161276932002260000001, 256036161276932002260000001607597862784080913990785121 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(12) has 1717 digits. - Michael S. Branicky, Feb 25 2021

LINKS

Michael S. Branicky, Table of n, a(n) for n = 1..11 (terms 1..10 from Hiroaki Yamanouchi)

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(2)

(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(2)

(Python)

from math import isqrt

def anext(an):

  lo, hi = an*10, an*10 + 9

  while True:

    found = False

    if isqrt(hi)**2 > lo: return (isqrt(lo)+1)**2

    lo, hi = lo*10, hi*10 + 9

n, an = 1, 2

for n in range(2, 17):

  an = anext(an)

  print(n, an) # Michael S. Branicky, Feb 25 2021

CROSSREFS

Cf. A048559, A048561.

Sequence in context: A042919 A229975 A174970 * A085830 A270346 A212022

Adjacent sequences:  A249890 A249891 A249892 * A249894 A249895 A249896

KEYWORD

nonn,base

AUTHOR

Derek Orr, Nov 08 2014

STATUS

approved

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Last modified May 20 08:03 EDT 2022. Contains 353852 sequences. (Running on oeis4.)