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A272208 Numbers n such that n immediately follows the decimal point in the base-10 representation of sqrt(n). 1
8, 77, 5711, 9797, 997997, 8053139, 60755907, 99979997, 9999799997, 71515443427, 93445113269, 999997999997, 26369408771424, 96872443448748, 99650905131203, 99999979999997, 751273714618266, 3368237924952647, 3493498117381256, 9999999799999997, 35399255736521405, 999999997999999997 (list; graph; refs; listen; history; text; internal format)
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 A202732

Adjacent sequences:  A272205 A272206 A272207 * A272209 A272210 A272211

KEYWORD

nonn,base,hard

AUTHOR

David W. Wilson, May 15 2016

STATUS

approved

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Last modified June 24 11:45 EDT 2021. Contains 345416 sequences. (Running on oeis4.)