A247947 Four-digit odd semiprimes with all digits distinct.

1027, 1037, 1043, 1047, 1057, 1059, 1067, 1073, 1079, 1203, 1205, 1207, 1243, 1247, 1253, 1257, 1263, 1267, 1273, 1285, 1293, 1329, 1345, 1347, 1349, 1357, 1369, 1379, 1385, 1387, 1389, 1397, 1403, 1405, 1437, 1457, 1465, 1469, 1473, 1497, 1507, 1509, 1527, 1529

Offset: 1

Author

K. D. Bajpai, Sep 27 2014

Keywords

• nonn
• base
• fini
• full

Comments

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.

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

Examples

			a(1) = 1027 = 13 * 79 is the smallest four-digit odd semiprime with all digits distinct.
a(863) = 9865 = 5 * 1973 is the largest four-digit odd semiprime with all digits distinct.
		

Links

• K. D. Bajpai, Table of n, a(n) for n = 1..863

Crossrefs

Cf. A001358, A046315, A074673, A235690.

Programs

Mathematica

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