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A060291
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Number of twin Harshads, including overlaps, whose sum is prime and where the 2nd Harshad is <= 10^n.
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0
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OFFSET
| 1,1
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FORMULA
| Generate the twin Harshads whose sum is prime. Count how many there are where the 2nd Harshad in the pair is <= to a consecutive power of 10
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EXAMPLE
| a(1)=7 because there are 7 pairs of Harshads whose sum is prime and the 2nd Harshad in the pair is <= 10; these are 1+2=3, 2+3=5, 3+4=7, 5+6=11, 6+7=13, 8+9=17, 9+10=19. (Another sequence does not permit overlapping Harshad numbers.)
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CROSSREFS
| Cf. A060288-A060290, A005349, A060159.
Sequence in context: A143504 A152043 A181585 * A132899 A051175 A058537
Adjacent sequences: A060288 A060289 A060290 * A060292 A060293 A060294
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KEYWORD
| more,nonn,base
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AUTHOR
| Enoch Haga (Enokh(AT)comcast.net), Mar 24 2001
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