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A168515 Primes n that are concatenation of four 2-digit primes in decreasing order. 0
29231311, 37231913, 37311913, 41231713, 41291311, 41291713, 41292311, 41292319, 41311913, 41312911, 41312923, 41372311, 41372911, 43191311, 43231711, 43311713, 43311911, 43371917, 43412911, 47231311, 47231711 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

n = 10^6*p+10^4*q+10^2*r+s, with primes p,q,r,s, 98>p>q>r>s>10.

There are 722 such primes from 29231311,37231913,37311913 to

97897931,97897973,97898347.

LINKS

Table of n, a(n) for n=1..21.

MATHEMATICA

pr2={97, 89, 83, 79, 73, 71, 67, 61, 59, 53, 47, 43, 41, 37, 31, 29, 23, 19, 17, 13, 11};

k=4; ssk=Subsets[pr2, {k}]; Le=Binomial[21, k];

Reap[Do[If[PrimeQ[fd=FromDigits[Flatten[IntegerDigits/@ssk[[i]]]]], Sow[fd]], {i, Le}]][[2, 1]]

CROSSREFS

Cf. A168499, A168500, A168513.

Sequence in context: A198172 A176141 A105013 * A287384 A107619 A320723

Adjacent sequences:  A168512 A168513 A168514 * A168516 A168517 A168518

KEYWORD

base,fini,full,nonn

AUTHOR

Zak Seidov, Nov 28 2009

STATUS

approved

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Last modified October 21 15:18 EDT 2021. Contains 348155 sequences. (Running on oeis4.)