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A145713
Number of primes p in the range 9 < p <= prime(10^n) that begin and end with the same digit.
4
1, 10, 105, 1180, 14143, 158036, 1703161, 17520558, 157563619, 1431557207
OFFSET
1,2
FORMULA
a(n) = A145709(n) + A145710(n) + A145711(n) + A145712(n). [R. J. Mathar, Aug 02 2010]
EXAMPLE
The initial 1 is from the prime 11.
a(4)=1180 because to 10^4 or 10000 primes, ending in 104729=A006988(4), there are 1180 primes with equal and distinct first and last digits: 1 and 1, 3 and 3, 7 and 7 and 9 and 9.
CROSSREFS
Sequence in context: A068767 A233830 A046715 * A123512 A079515 A024131
KEYWORD
hard,more,nonn,base
AUTHOR
Enoch Haga, Oct 16 2008
EXTENSIONS
Edited by N. J. A. Sloane, Aug 16 2010
a(6) corrected and a(7)-a(10) added by D. S. McNeil, Aug 29 2010
STATUS
approved