OFFSET
1,1
COMMENTS
The first term congruent to 2 mod 9 is a(2729) = 29999. - Robert Israel, Jul 07 2015
Among first 10000 terms, numbers of terms congruent to {0..8} mod 9 are: {1,425,139,1453,2773,1233,1252,3087,2739}. Terms with minimal digitsum = 4 are: {4,22,121,202,301,1003,1111,2101,10003, 10021,10102,10201,11002,11101,12001,30001,100021,100102,100201,101011, 110002,110101,111001}. Is this subsequence infinite? - Zak Seidov, Jul 07 2015
LINKS
Zak Seidov, Table of n, a(n) for n = 1..10000
EXAMPLE
55 is in the sequence because (1) it is a semiprime and (2) the sum of its digits 5+5=10 is also a semiprime.
MAPLE
select(t -> map(numtheory:-bigomega, [t, convert(convert(t, base, 10), `+`)])=[2, 2], [$1..1000]); # Robert Israel, Jul 07 2015
MATHEMATICA
Select[Range[514], PrimeOmega[{Total[IntegerDigits[#]], #}]=={2, 2}&] (* Zak Seidov, Jul 07 2015 *)
PROG
(PARI) A007953(n)= { local(resul); resul=0; while(n>0, resul += n%10; n = (n-n%10)/10; ); return(resul); } { for(n=4, 600, if( bigomega(n)==2, if(bigomega(A007953(n)) == 2, print1(n, ", "); ); ); ); } \\ R. J. Mathar, May 23 2006
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), May 20 2006
EXTENSIONS
Corrected by R. J. Mathar, May 23 2006
STATUS
approved