A128759 - OEIS

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A128759

Least k such that the Jacobsthal function A048669(k) = n.

1, 2, 15, 6, 105, 30, 1155, 770, 36465, 210, 15015, 6006, 255255, 2310, 8580495, 102102, 4849845, 72930, 20056049013, 74364290, 5898837945, 30030, 3234846615, 881790, 195282582495, 510510, 218257003965, 20281170, 100280245065, 17160990, 934482952262145, 6614136163635

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OFFSET

1,2

COMMENTS

Except for a(1) and a(2), the same as A070971. It appears that a(2n)=2a(n) for odd n. Because the primorial numbers (A002110) yield record values of the Jacobsthal function, we have a(A048670(n))=A002110(n). Note that numbers in this sequence up to n=18 have the form p#, p#/2, p#/q, or p#/(2q), where p and q are primes with 2<q<p and p# denotes the product of the primes up to p.

LINKS

Table of n, a(n) for n=1..32.

CROSSREFS

Cf. A048669, A070971, A002110, A048670.

Sequence in context: A371895 A371340 A363483 * A066582 A111329 A344889

Adjacent sequences: A128756 A128757 A128758 * A128760 A128761 A128762

KEYWORD

nonn

AUTHOR

T. D. Noe, Mar 28 2007

EXTENSIONS

a(19) onwards from Don Reble, Oct 17 2013

STATUS

approved