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A124450 Lesser of a pair of not necessarily distinct closest n-digit primes that add up to 10^n. +0
5
5, 47, 491, 4919, 49877, 499943, 4999913, 49999757, 499999931, 4999999937, 49999999811, 499999999769, 4999999998431, 49999999999619, 499999999999769, 4999999999998557, 49999999999998887, 499999999999999679 (list; graph; listen)
OFFSET

1,1

LINKS

Hans Havermann, Table of n, a(n) for n = 1..50

FORMULA

10^n - a(n) is prime.

EXAMPLE

10^1=5+5; 10^2=47+53; 10^3=491+509;

10^4=4919+5081; 10^5=49877=50123; 10^6=499943+500057;

10^7=4999913+5000087; 10^8=49999757+50000243;

10^9=499999931+500000069;

10^10=4999999937+5000000063}, etc.

MATHEMATICA

Table[ h =10^n/2; c=0; While[ PrimeQ[ h-c ]==False || PrimeQ[ h+c ]==False, c++ ]; h-c, {n, 1, 50} ] (from Hans Havermann, Nov 02 2006)

CROSSREFS

Cf. A065577 = number of Goldbach partitions of 10^n.

Cf. A124013.

Sequence in context: A122501 A049281 A124267 this_sequence A136023 A074192 A058806

Adjacent sequences: A124447 A124448 A124449 this_sequence A124451 A124452 A124453

KEYWORD

nonn

AUTHOR

Zak Seidov (zakseidov(AT)yahoo.com), Nov 02 2006

EXTENSIONS

Edited by N. J. A. Sloane (njas(AT)research.att.com) May 15 2008 at the suggestion of R. J. Mathar.

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Last modified November 27 22:38 EST 2009. Contains 167602 sequences.


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