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Search: id:A087632
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| A087632 |
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Number of n-digit primes == 7 (mod 10). E.g. there exist 5 two-digit prime numbers(17,37,47,67 and 97) with unit's place 7. |
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+0
1
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| 1, 5, 40, 262, 2103, 17210, 146590, 1274284, 11271819, 101051725
(list; graph; listen)
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OFFSET
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0,2
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EXAMPLE
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E.g. a(3)=40, since there are 40 three-digit numbers with unit place digit as 7.
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PROGRAM
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(JAVA) The terms of the sequences are generated by changing the range for j for the various number of digits. E.g. it ranges from 100 to 999 for three-digit numbers. float r, x; int c=0, count=0; for (float j=100f; j<1000f; j++) { for (float i=2f; i<j; i++) { r=j%i; if (r==0) c=1; } if (c == 0) { x=j%10; if (x==7) count=count+1; } c=0; } System.out.println("count = "+count);
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CROSSREFS
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Sequence in context: A054604 A157794 A001656 this_sequence A124306 A124545 A125729
Adjacent sequences: A087629 A087630 A087631 this_sequence A087633 A087634 A087635
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KEYWORD
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nonn
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AUTHOR
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Meenakshi Srikanth and Amarnath Murthy (menakan_s(AT)yahoo.com), Sep 15 2003
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EXTENSIONS
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More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net), Oct 04 2003
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