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A337428 a(n) is the least prime of the form (3^r*5^s*7^t + 1)/2, r, s, t > 0, r + s + t = n. 2
53, 263, 1103, 6563, 4253, 49613, 38273, 1041863, 344453, 60775313, 109395563, 119601563, 151903553, 325507613, 3797588813, 202622460863, 17437907813, 11299764263, 20339575673, 282494106563, 1186475247563, 5932376237813, 29661881189063, 8237528147363, 14827550665253 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

LINKS

David A. Corneth, Table of n, a(n) for n = 3..506

EXAMPLE

a(3) = 53: (3*5*7+1)/2 = 106/2 is prime.

a(4) = 263: The first choice of exponents leads to the composite (3^2*5*7+1)/2 = 158, but the next choice (3*5^2*7+1)/2 = 526/2 is prime.

PROG

(PARI) seqpp (3, 3, 1, 27) \\ using function seqpp defined in A337427

CROSSREFS

Cf. A337423, A337425, A337427.

Sequence in context: A036911 A241488 A140851 * A253119 A253112 A211146

Adjacent sequences: A337425 A337426 A337427 * A337429 A337430 A337431

KEYWORD

nonn

AUTHOR

Hugo Pfoertner, Aug 29 2020

STATUS

approved

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Last modified February 1 07:16 EST 2023. Contains 359981 sequences. (Running on oeis4.)