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A320969 Semiprimes with distinct digits. 0
4, 6, 9, 10, 14, 15, 21, 25, 26, 34, 35, 38, 39, 46, 49, 51, 57, 58, 62, 65, 69, 74, 82, 85, 86, 87, 91, 93, 94, 95, 106, 123, 129, 134, 142, 143, 145, 146, 158, 159, 169, 178, 183, 185, 187, 194, 201, 203, 205, 206, 209, 213, 214, 215, 217, 218, 219, 235, 237, 247, 249, 253, 254, 259, 265, 267, 274 (list; graph; refs; listen; history; text; internal format)
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

Table of n, a(n) for n=1..67.

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.

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

Intersection of A001358 and A010784.

Cf. A029743.

Sequence in context: A046368 A236108 A253106 * A113433 A115654 A036326

Adjacent sequences:  A320966 A320967 A320968 * A320970 A320971 A320972

KEYWORD

nonn,base,fini

AUTHOR

Zak Seidov, Oct 25 2018

EXTENSIONS

More terms from M. F. Hasler, Oct 29 2018

STATUS

approved

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Last modified March 5 13:58 EST 2021. Contains 341823 sequences. (Running on oeis4.)