This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A247947 Four-digit odd semiprimes with all digits distinct. 3
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 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. LINKS K. D. Bajpai, Table of n, a(n) for n = 1..863 EXAMPLE 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. MATHEMATICA c = 0; Do[If[Length[Union[IntegerDigits[n]]] == 4 && PrimeOmega[n] == 2, c++; Print[c, "  ", n]], {n, 1001, 9999, 2}] CROSSREFS Cf. A001358, A046315, A074673, A235690. Sequence in context: A168153 A246245 A235692 * A066133 A119455 A252772 Adjacent sequences:  A247944 A247945 A247946 * A247948 A247949 A247950 KEYWORD nonn,base,fini,full AUTHOR K. D. Bajpai, Sep 27 2014 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 8 04:46 EST 2019. Contains 329853 sequences. (Running on oeis4.)