OFFSET
1,1
COMMENTS
Numbers of (2..6)-digit terms are 12,40,105,260,543. [From Zak Seidov, Apr 12 2009]
EXAMPLE
250 is a composite number whose digit sum of 7 is a single-digit prime.
MATHEMATICA
s={}; Do[t=Total[IntegerDigits[n]]; If[ !PrimeQ[n]&&(t-2)(t-3)(t-5)(t-7)== 0, AppendTo[s, n]], {n, 7*10^3}]; s [From Zak Seidov, Apr 12 2009]
CROSSREFS
KEYWORD
nonn,base,easy,less
AUTHOR
Parthasarathy Nambi, Apr 06 2009
EXTENSIONS
Extended, minor edits and keywords easy, less added by Klaus Brockhaus, Apr 12 2009
More terms from Zak Seidov, Apr 12 2009
STATUS
approved