OFFSET
0,3
LINKS
David A. Corneth, Table of n, a(n) for n = 0..998
FORMULA
EXAMPLE
For n=2 are counted the two '2's in { 2, 12 }.
MATHEMATICA
Array[Total@ DigitCount[Range[Sum[10^i - 1, {i, #}]/9], 10, 2] &, 7] (* Michael De Vlieger, Dec 31 2020 *)
PROG
(PARI) print1(c=N=0); for(n=1, 8, print1(", "c+=sum(k=N+1, N=N*10+n, #select(d->d==2, digits(k)))))
(PARI) A277832(n)=if(n<3, (n==2)*2, n<13, A277833(n)+4*10^(n-3), error("n > 12 not yet implemented")) \\ M. F. Hasler, Nov 02 2016, edited Dec 28 2020
(PARI) a(n) = {if(n == 0, return(0)); n = (10^(n+1)\9-n)\9; f(n, 2) }
f(n, {c = 2}) = { my(d = digits(n), res = 0); for(i = 1, #d - 1, res += d[i] * (#d - i)*10^(#d - i - 1); if(d[i]==c, res+=(n % (10^(#d - i)) + 1); ); if(d[i] > c, res+=(10^(#d - i)) ); ); if(d[#d] >= c, res++); res } \\ David A. Corneth, Dec 31 2020
CROSSREFS
KEYWORD
nonn,base
AUTHOR
M. F. Hasler, Nov 01 2016
EXTENSIONS
More terms from Lars Blomberg, Nov 05 2016
Removed incorrect b-file. - David A. Corneth, Dec 31 2020
STATUS
approved