A249897 a(n+1) is next smallest square not divisible by 10 beginning with a(n), initial term is 7.

7, 729, 729316, 7293164743396, 72931647433968832639882896, 72931647433968832639882896319584064899663299793041401

Offset: 1

Author

Derek Orr, Nov 08 2014

Keywords

• nonn
• base

Links

• Hiroaki Yamanouchi, Table of n, a(n) for n = 1..10

Crossrefs

Cf. A048559, A048561.

Programs

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)

Extensions

a(5)-a(6) corrected by Hiroaki Yamanouchi, Nov 17 2014