A161551 The smallest composite number larger than the n-th composite number, which has a sum of digits equal to the n-th composite number.

22, 15, 26, 18, 28, 39, 68, 69, 88, 99, 299, 399, 589, 699, 799, 899, 999, 2899, 3999, 5999, 6999, 7999, 9899, 9999, 29999, 39999, 58999, 69999, 89999, 99999, 299899, 399999, 499999, 689999, 699999, 889999, 999999, 1999999, 3899999, 3999999

Offset

1,1

Comments

Variant of A073866, where the requirement that a(n) > A002808(n) is dropped.

Links

Table of n, a(n) for n=1..40.

Formula

min{c in A002808, c> A002808(n): A007953(c) = A002808(n)}. - R. J. Mathar, Dec 06 2011

Example

The first composite is 4, and the first sum of digits is 13, but since that is prime, we go to the next, 22, which being composite is a(1).

Maple

A161551 := proc(n)
    for j from n+1 do
        if digsum(A002808(j)) = A002808(n) then
            return A002808(j) ;
        end if;
    end do:
end proc:
seq(A161551(n), n=1..30) ; # R. J. Mathar, Dec 06 2011

Prog

(UBASIC)
10 'compsdig, Enoch Haga, Jun 12 2009
20 N=1
30 Q=str(N)
40 L=len(Q)
50 for X=1 to L
60 M=str(mid(Q, X, 1)): Z=Z+val(mid(Q, X, 1))
70 next X
80 if Z=56 and Z<>prmdiv(Z) and N<>prmdiv(N) then print N: stop
90 Z=0: N=N+1: goto 30

Crossrefs

Cf. A075360, A054750.

Sequence in context: A040464 A266015 A070665 * A291428 A195927 A195930

Adjacent sequences: A161548 A161549 A161550 * A161552 A161553 A161554

Keyword

base,easy,nonn

Author

Enoch Haga, Jun 13 2009

Status

approved