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A034276 Smallest prime that generates a prime pyramid of height n. 3
11, 29, 2, 5, 41, 251, 43, 145577, 51941, 4372877, 26901631, 366636187, 15387286403, 218761753811, 3313980408469 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Let p be prime; look for the smallest prime in {1|p|1, 3|p|3, 7|p|7, 9|p|9}, where '|' stands for concatenation; repeat until no such prime can be found; then height(p) = number of rows in pyramid.

a(13) > 10^10. - Donovan Johnson, Aug 13 2010

LINKS

Table of n, a(n) for n=1..15.

H. Heinz, Patterns in Primes, Illustrating Two Prime Pyramids

Chai Wah Wu, On a conjecture regarding primality of numbers constructed from prepending and appending identical digits, arXiv:1503.08883 [math.NT], 2015.

EXAMPLE

Example for p=43: 43 3433 334333 93343339 3933433393 939334333939 39393343339393, stop; height(43)=7.

CROSSREFS

Cf. A047076, A053600, A052205, A256957, A052091, A052092.

Sequence in context: A061086 A201633 A274130 * A245169 A323822 A196357

Adjacent sequences:  A034273 A034274 A034275 * A034277 A034278 A034279

KEYWORD

nonn,nice,base,more

AUTHOR

Felice Russo, Jan 25 2000

EXTENSIONS

More terms from Naohiro Nomoto, Jul 14 2001

a(11)-a(12) from Donovan Johnson, Aug 13 2010

a(13) from Chai Wah Wu, Apr 10 2015

a(14)-a(15) from Giovanni Resta, May 15 2020

STATUS

approved

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Last modified October 27 01:02 EDT 2020. Contains 338035 sequences. (Running on oeis4.)