A322648 Number of times the digit 7 appears in the first 10^n decimal digits of sqrt(2), sometimes called Pythagoras's constant, counting after the decimal point.

0, 18, 104, 964, 10008, 100008, 999359, 9998646, 99980315, 999986743

Offset

1,2

Comments

It is not known if sqrt(2) is normal, but the distribution of decimal digits found for the first 10^n digits of sqrt(2) shows no statistically significant departure from a uniform distribution.

Links

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

Eric Weisstein's World of Mathematics, Pythagoras's Constant Digits.

Maple

a:=proc(n)
  local digits, SQRT2, C, i;
  digits:=10^n+100;
  SQRT2:=convert(frac(evalf[digits](sqrt(2))), string)[2..digits-99];
  C:=0;
  for i from 1 to length(SQRT2) do
    if SQRT2[i]="7" then C:=C+1; fi;
  od;
  return(C);
end;

Mathematica

Table[DigitCount[IntegerPart[(Sqrt[2]-1)*10^10^n], 10, 7], {n, 1, 10}] (* Robert Price, Mar 29 2019 *)

Crossrefs

Cf. A002193, A099298, A322641, A322642, A322643, A322644, A322645, A322646, A322647, A322649, A322650.

Sequence in context: A223241 A197339 A304763 * A285854 A123277 A123595

Adjacent sequences: A322645 A322646 A322647 * A322649 A322650 A322651

Keyword

nonn,base,more

Author

Martin Renner, Dec 21 2018

Status

approved