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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..10.

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

Cf. A145709 - A145712

Sequence in context: A068767 A233830 A046715 * A123512 A079515 A024131

Adjacent sequences:  A145710 A145711 A145712 * A145714 A145715 A145716

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

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Last modified November 20 04:05 EST 2017. Contains 294959 sequences.