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A076886 Smallest palindrome with exactly n prime factors (counted with multiplicity). 2
1, 2, 4, 8, 88, 252, 2772, 27872, 2112, 4224, 8448, 44544, 48384, 2977792, 27011072, 405504, 4091904, 441606144, 405909504, 886898688, 677707776, 4285005824, 276486684672, 21128282112, 633498894336, 2701312131072, 8691508051968 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..26.

EXAMPLE

a(4)=88 because 88 is the smallest palindromic number with 4 prime factors, 2^3*11 (counted with multiplicity).

MATHEMATICA

f[n_] := Length[ Flatten[ Table[ # [[1]], { # [[2]]}] & /@ FactorInteger[n]]]; a = Table[0, {50}]; Do[b = IntegerDigits[n]; c = FromDigits[ Join[b, Drop[ Reverse[b], 1]]]; d = FromDigits[ Join[ b, Reverse[b]]]; e = f[c]; If[ a[[e + 1]] == 0 || a[[e + 1]] > c, a[[e + 1]] = c]; e = f[d]; If[ a[[e + 1]] == 0 || a[[e + 1]] > d, a[[e + 1]] = d], {n, 1, 18697304}]

CROSSREFS

Sequence in context: A088114 A239697 A237913 * A309565 A046385 A068664

Adjacent sequences:  A076883 A076884 A076885 * A076887 A076888 A076889

KEYWORD

base,nonn

AUTHOR

Shyam Sunder Gupta, Nov 25 2002

EXTENSIONS

Edited and extended by Robert G. Wilson v, Dec 02 2002

STATUS

approved

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Last modified November 13 17:34 EST 2019. Contains 329106 sequences. (Running on oeis4.)