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 A281592 Products of three distinct primes p1, p2 and p3 (sphenic numbers) with p1
 138, 777, 4642, 10258, 10263, 12207, 13282, 16167, 19762, 30783, 37407, 38482, 46978, 48927, 56127, 60145, 63543, 73767, 81687, 89823, 95367, 95627, 103863, 110905, 115527, 128545, 202705, 208879, 223643, 284119, 324947, 325793, 360151, 395003, 477538, 541163, 558322, 585538, 672199, 673693, 780082, 914551, 1016643 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 10258 is in the sequence because 10258 = 2*23*223 and 223 is the concatenation of 2 with 23. MATHEMATICA c[x_, y_] := x 10^IntegerLength[y] + y; upto[mx_] := Sort@ Reap[Block[{p=2, q=3, v=1}, While[v <= mx, While[p < q && (v = p q (r = c[p, q])) <= mx, If[PrimeQ@r, Sow@v]; p = NextPrime[p]]; p=2; q = NextPrime[q]; v = p q c[p, q]]]][[2, 1]]; upto[10^6] (* Giovanni Resta, Apr 14 2017 *) PROG (PARI) isok(n) = f = factor(n); ((#f~ == 3) && (vecmax(f[, 2]) == 1) && (f[3, 1] == fromdigits(concat(digits(f[1, 1]), digits(f[2, 1]))))); \\ Michel Marcus, Apr 14 2017 CROSSREFS Cf. A007304, A133980 (the p3 primes). Sequence in context: A168531 A260133 A317579 * A213963 A279964 A163693 Adjacent sequences:  A281589 A281590 A281591 * A281593 A281594 A281595 KEYWORD nonn,base AUTHOR Peter Weiss, Apr 14 2017 STATUS approved

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Last modified December 4 12:55 EST 2021. Contains 349525 sequences. (Running on oeis4.)