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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.
2
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.
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
Sequence in context: A040464 A266015 A070665 * A291428 A195927 A195930
KEYWORD
base,easy,nonn
AUTHOR
Enoch Haga, Jun 13 2009
STATUS
approved