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

Author

Enoch Haga, Jun 13 2009

Keywords

• base
• easy
• nonn

Comments

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

Examples

			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).
		

Crossrefs

Cf. A075360, A054750.

Programs

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

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

Formula

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