A272208 Numbers n such that n immediately follows the decimal point in the base-10 representation of sqrt(n).

8, 77, 5711, 9797, 997997, 8053139, 60755907, 99979997, 9999799997, 71515443427, 93445113269, 999997999997, 26369408771424, 96872443448748, 99650905131203, 99999979999997, 751273714618266, 3368237924952647, 3493498117381256, 9999999799999997, 35399255736521405, 999999997999999997

Offset

1,1

Comments

Sequence includes all numbers of form (10^n-3)(10^n+1) for n >= 1, hence is infinite.

Links

David W. Wilson, Table of n, a(n) for n = 1..27

Example

5711 immediately follows the decimal in sqrt(5711) = 75.5711+, so 5711 is in the sequence.
77327 does not immediately follow the decimal in sqrt(77327) = 278.077327+, so 77327 is not in this sequence.

Prog

(PARI) is(n)=my(t=10^#Str(n)); sqrtint(t^2*n)%t==n \\ Charles R Greathouse IV, May 16 2016

Crossrefs

Strict subsequence of A074841.

Sequence in context: A196071 A304303 A074841 * A136954 A328467 A347322

Adjacent sequences: A272205 A272206 A272207 * A272209 A272210 A272211

Keyword

nonn,base,hard

Author

David W. Wilson, May 15 2016

Status

approved