A130225 a(1) = 2; a(n) = a(n-1) + (number of times the digit 2 has appeared in the sequence so far).

2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 18, 20, 23, 27, 32, 38, 44, 50, 56, 62, 69, 76, 83, 90, 97, 104, 111, 118, 125, 133, 141, 149, 157, 165, 173, 181, 189, 197, 205, 214, 224, 236, 249, 263, 278, 294, 311, 328, 346, 364, 382, 401, 420, 440, 460, 480, 500, 520

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Maple

A130225 := proc(n)
    option remember;
    if n = 1 then
        2;
    else
        a := procname(n-1) ;
        for j from 1 to n-1 do
            for d in convert(procname(j), base, 10) do
                if d = 2 then
                    a := a+1 ;
                end if;
            end do:
        end do:
        a ;
    end if;
end proc:
seq(A130225(n), n=1..80) ; # R. J. Mathar, Aug 06 2016

Mathematica

nxt[{t_, a_}]:=Module[{k=a+t}, {t+DigitCount[k, 10, 2], k}]; NestList[nxt, {1, 2}, 60][[All, 2]] (* Harvey P. Dale, Jun 03 2021 *)

Crossrefs

Sequence in context: A008730 A033064 A246074 * A096902 A246081 A117325

Adjacent sequences: A130222 A130223 A130224 * A130226 A130227 A130228

Keyword

base,easy,nonn

Author

Eric Angelini, Aug 05 2007

Status

approved