OFFSET
1,1
COMMENTS
This sequence has 864939 terms, the last being 987654301.
Number of n-digit terms, for n = 1..9: 3, 27, 183, 1140, 6240, 27666, 99543, 277146, 452991. There are no semiprimes with distinct digits for n > 9.
Indeed, a 10-digit pandigital number is divisible by 9=3*3, so it can't be semiprime, and there are not more than 10 distinct digits in base 10. - M. F. Hasler, Oct 29 2018
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
a(n*10^5) for n= 1..8: 6710843 = 173*38791, 30541627 = 881*34667, 62148035 = 5*12429607, 95068217 = 41*2318737, 280196547 = 3*93398849, 476891503 = 11*43353773, 654037129 = 79*8278951, 861247059 = 3*287082353.
MATHEMATICA
Select[Range[300], PrimeOmega[#]==2&&Max[DigitCount[#]]==1&] (* Harvey P. Dale, Jan 29 2022 *)
PROG
(PARI) is(n)=bigomega(n)==2&& #Set(n=digits(n))=#n \\ M. F. Hasler, Oct 29 2018
(PARI) row(n, L=List())=forvec(d=vector(n, i, [0, 9]), for(i=!d[1]*(n-1)!, n!-1, bigomega(fromdigits(vecextract(d, numtoperm(n, i))))==2||next; listput(L, fromdigits(vecextract(d, numtoperm(n, i))))), 2); Set(L) \\ Returns the n-digit terms. - M. F. Hasler, Oct 29 2018
CROSSREFS
KEYWORD
nonn,base,fini
AUTHOR
Zak Seidov, Oct 25 2018
EXTENSIONS
More terms from M. F. Hasler, Oct 29 2018
STATUS
approved