

A052092


Lengths of the palindromic primes from Honaker's sequence A053600.


5



1, 3, 5, 9, 11, 15, 19, 23, 25, 31, 35, 41, 45, 49, 55, 59, 63, 69, 75, 81, 87, 93, 99, 105, 109, 113, 119, 125, 129, 133, 139, 145, 151, 157, 161, 167, 173, 179, 185, 191, 195, 201, 207, 213, 219, 225, 231, 237, 243, 249, 255, 261, 267, 273, 279, 285, 291, 297
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OFFSET

0,2


COMMENTS

Since the terms from a(34) onward are currently only probable primes, the lengths given in this sequence beyond that point are only provisional.
For n > 0, a(n) = a(n1)+2*m where m is the number of digits of A052091(n).  Chai Wah Wu, Dec 03 2015


LINKS

Chai Wah Wu, Table of n, a(n) for n = 0..501


PROG

(Python)
from sympy import isprime
A052092_list, l, p = [1], 1, 2
for _ in range(100):
m, ps = 1, str(p)
s = int('1'+ps+'1')
while not isprime(s):
m += 1
ms = str(m)
if ms[0] in '268':
ms = str(int(ms[0])+1) + '0'*(len(ms)1)
m = int(ms)
if ms[0] in '45':
ms = '7' + '0'*(len(ms)1)
m = int(ms)
s = int(ms+ps+ms[::1])
p = s
l += 2*len(ms)
A052092_list.append(l) # Chai Wah Wu, Dec 02 2015


CROSSREFS

Cf. A052091, A053600, A047076.
Sequence in context: A287421 A214214 A281505 * A075991 A292918 A216091
Adjacent sequences: A052089 A052090 A052091 * A052093 A052094 A052095


KEYWORD

nonn,base


AUTHOR

Patrick De Geest, Jan 15 2000


EXTENSIONS

Comments from G. L. Honaker, Jr., Mar 30 2000
Edited by T. D. Noe, Oct 30 2008


STATUS

approved



