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A046380 Palindromes with exactly 6 palindromic prime factors (counted with multiplicity). 1
2772, 6776, 25452, 59895, 88788, 549945, 1931391, 8117118, 8447448, 51033015, 52711725, 58344385, 103838301, 535707535, 620434026, 1663223661, 8262112628, 15271417251, 25227972252, 27747974772, 27974547972, 92628082629, 97079897079, 6421339331246, 8401825281048 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..49

PROG

(Python)

from sympy import factorint

def palQgen10(l): # generator of palindromes in base 10 of length <= 2*l

....if l > 0:

........yield 0

........for x in range(1, l+1):

............for y in range(10**(x-1), 10**x):

................s = str(y)

................yield int(s+s[-2::-1])

............for y in range(10**(x-1), 10**x):

................s = str(y)

................yield int(s+s[::-1])

A046380_list = []

for x in palQgen10(6):

....a = factorint(x)

....if sum(list(a.values())) == 6:

........for p in a:

............s = str(p)

............if s != s[::-1]:

................break

........else:

............A046380_list.append(x) # Chai Wah Wu, Dec 26 2014

CROSSREFS

Cf. A046332.

Sequence in context: A205418 A231709 A046332 * A249228 A154081 A099691

Adjacent sequences:  A046377 A046378 A046379 * A046381 A046382 A046383

KEYWORD

nonn,more,base

AUTHOR

Patrick De Geest, Jun 15 1998

EXTENSIONS

a(19)-a(25) from Chai Wah Wu, Dec 26 2014

STATUS

approved

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Last modified September 23 23:21 EDT 2018. Contains 315306 sequences. (Running on oeis4.)