OFFSET
1,14
COMMENTS
For n > 1: if A023961(n)=7 then a(n) = a(n-1) + 1, otherwise a(n) = a(n-1).
Lim_{n->infinity} a(n)/n = 1/10.
REFERENCES
G. Pólya and G. Szegő, Problems and Theorems in Analysis I (Springer 1924, reprinted 1972), Part Two, Chap. 4, Sect. 4, Problem 178.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
a(10) = 1, a(100) = 11, a(1000) = 99, a(10000) = 1010.
MATHEMATICA
Accumulate[Table[If[NumberDigit[Sqrt[n], -1]==7, 1, 0], {n, 120}]] (* Harvey P. Dale, Apr 20 2022 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Reinhard Zumkeller, Aug 20 2005
STATUS
approved