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A060289
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Number of distinct (non-overlapping) twin Harshad numbers whose sum is prime and where the 2nd Harshad is <= 10^n.
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2
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OFFSET
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0,1
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LINKS
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Table of n, a(n) for n=0..6.
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FORMULA
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Generate the twin Harshads whose sum is prime. Count how many there are where the 2nd Harshad in the pair is <= a consecutive power of 10.
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EXAMPLE
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a(0)=4 because there are four pairs of Harshads whose sum is prime and the 2nd Harshad in the pair is <=10; these are 1+2=3, 3+4=7, 5+6=11, 9+10=19. 8+9=17 is not included because this pair overlaps 7+8=15, which also happens to be not prime. (Another sequence might include such overlapping pairs.)
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CROSSREFS
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A060288, A005349, A060159.
Sequence in context: A061806 A119997 A010361 * A215024 A066879 A134750
Adjacent sequences: A060286 A060287 A060288 * A060290 A060291 A060292
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KEYWORD
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easy,more,nonn,base
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AUTHOR
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Enoch Haga, Mar 23 2001
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STATUS
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approved
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