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A247947 Four-digit odd semiprimes with all digits distinct. 3

%I

%S 1027,1037,1043,1047,1057,1059,1067,1073,1079,1203,1205,1207,1243,

%T 1247,1253,1257,1263,1267,1273,1285,1293,1329,1345,1347,1349,1357,

%U 1369,1379,1385,1387,1389,1397,1403,1405,1437,1457,1465,1469,1473,1497,1507,1509,1527,1529

%N Four-digit odd semiprimes with all digits distinct.

%C There are exactly 863 four-digit odd semiprimes with all distinct digits. The last few terms of the sequence are: 9563, 9571, 9573, 9607, 9617, 9627, 9637, 9641, 9647, 9651, 9671, 9673, 9683, 9687, 9701, 9703, 9713, 9731, 9745, 9753, 9761, 9763, 9813, 9827, 9841, 9847, 9853, 9863, 9865.

%C See the link with the b-file for all 863 entries.

%H K. D. Bajpai, <a href="/A247947/b247947.txt">Table of n, a(n) for n = 1..863</a>

%e a(1) = 1027 = 13 * 79 is the smallest four-digit odd semiprime with all digits distinct.

%e a(863) = 9865 = 5 * 1973 is the largest four-digit odd semiprime with all digits distinct.

%t c = 0; Do[If[Length[Union[IntegerDigits[n]]] == 4 && PrimeOmega[n] == 2, c++; Print[c, " ", n]], {n, 1001, 9999, 2}]

%Y Cf. A001358, A046315, A074673, A235690.

%K nonn,base,fini,full

%O 1,1

%A _K. D. Bajpai_, Sep 27 2014

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Last modified January 29 14:07 EST 2020. Contains 331338 sequences. (Running on oeis4.)