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A135946 Number of primes with 3n digits made of adjacent primes with 3 digits. 2
143, 2753, 415639, 36573197 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Number of primes of the form: ... ddd3ddd2ddd1ddd0 = ddd0 * 10^0 + ddd1 * 10^3 + ddd2 * 10^6 + ddd3 * 10^9 + ..., where ddd0, ddd1, ddd2, ddd3, ... are prime with 3 digits. The i-th element of the sequence is the number of primes with i * 3 digits.

Approximation for the sum of the sequence up to a(k) for large values of k: Sum_{i=1..k} a(i) = 10^(3*k) / (3*k*log(10)) * (143/1000)^(k-1).

LINKS

Table of n, a(n) for n=1..4.

EXAMPLE

Example: a(2) = 2753 because there are 2753 numbers of the form ddd1ddd0 with ddd0, ddd1 prime numbers, i.e.: 101107, 101113, 101149, 101173, 101197, 101281, 101293, ..., 997991.

CROSSREFS

Cf. A135944, A135945.

Sequence in context: A185514 A220292 A159054 * A217534 A279115 A199039

Adjacent sequences:  A135943 A135944 A135945 * A135947 A135948 A135949

KEYWORD

nonn,base,bref

AUTHOR

Giorgio Balzarotti & Paolo P. Lava, Dec 07 2007

EXTENSIONS

a(4) from Donovan Johnson, Apr 17 2010

STATUS

approved

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Last modified May 20 01:46 EDT 2022. Contains 353847 sequences. (Running on oeis4.)