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A308899 a(n) = largest prime factor of the number with decimal expansion 20305070...0p_n where p_n = n-th prime. 1
2, 29, 131, 33287, 17627, 1754975809, 59218567, 318879703697, 2030507011013017019023, 14400758943354730631369, 1016015647, 32002443156997, 2464082401591041689, 4916481866859605372937116297910511, 2030507011013017019023029031037041043047 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The Honaker-Caldwell link gives a(25) =
20305070110130170190230290310370410430470530590
\61067071073079083089097,
with 70 digits.
LINKS
G. L. Honaker, Jr. and Chris Caldwell, Prime Curios!, 2030507...[70 digits]...89097.
EXAMPLE
Here are Maple's factorizations of 2, 203, 20305, ... (the factors appear in random order):
2 = (2)
203 = (7) (29)
20305 = (5) (31) (131)
2030507 = (61) (33287)
2030507011 = (13) (17627) (8861)
2030507011013 = (13) (89) (1754975809)
2030507011013017 = (59218567) (34288351)
2030507011013017019 = (7) (547) (1663) (318879703697)
MATHEMATICA
Table[FactorInteger[FromDigits[Flatten[IntegerDigits/@Riffle[Prime[Range[n]], 0]]]][[-1, 1]], {n, 20}] (* Harvey P. Dale, May 09 2021 *)
PROG
(PARI) pp = 0; forprime (p=2, 47, print1 (vecmax(factor(pp = pp * 10^(1+#digits(p)) + p)[, 1]~) ", ")) \\ Rémy Sigrist, Jul 13 2019
CROSSREFS
Inspired by the comment in Bernard Schott's A309101.
Sequence in context: A123004 A062618 A128842 * A028883 A024200 A137625
KEYWORD
nonn,base
AUTHOR
N. J. A. Sloane, Jul 13 2019
EXTENSIONS
More terms from Rémy Sigrist, Jul 13 2019
STATUS
approved

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Last modified May 25 01:50 EDT 2024. Contains 372782 sequences. (Running on oeis4.)