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A191587 Smallest prime p such that p-n is the product of exactly n distinct primes. 2
3, 17, 73, 1789, 6011, 1616621, 2114977, 111546443, 2156564419, 742073813491, 784009188701, 3093211012526647, 1240404920534023, 3206211009211419509, 171718219950879367781, 993969333554296364281, 6899316550553351234327, 108706781456610360939660763, 29365306848773629524600829, 376147205196163170923414109869 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..20.

EXAMPLE

a(4) = 1789 because 1789 - 4 = 1785 = 3 * 5 * 7 * 17.

MAPLE

A191587 := proc(n) for i from 1 do p := ithprime(i) ; if A001221(p-n) = n then return p ; end if; end do: end proc: # R. J. Mathar, Jul 01 2011

MATHEMATICA

Table[k := 2; While[Not[Length[FactorInteger[Prime[k] - n]] == n], k++ ]; Prime[k], {n, 1, 8}]

PROG

(PARI) A191587List(m) = local(j=1, p); for(n=1, m, p=prime(j); while(omega(p-n)!=n, p=prime(j++)); print1(p, ", "));

default(primelimit, 2200000); A191587List(7); \\ Klaus Brockhaus, Jun 21 2011

(Haskell)

a191587 n = head [p | p <- dropWhile (<= n) a000040_list,

a001221 (p - n) == n]

-- Reinhard Zumkeller, Jun 24 2015

CROSSREFS

Cf. A097977.

Cf. A000040, A001221.

Sequence in context: A342365 A179596 A339647 * A290411 A142868 A171875

Adjacent sequences: A191584 A191585 A191586 * A191588 A191589 A191590

KEYWORD

nonn,hard

AUTHOR

Michel Lagneau, Jun 07 2011

EXTENSIONS

a(10)-a(16) from Donovan Johnson, Jan 14 2012

a(17)-a(20) from Robert Israel, Mar 27 2020

STATUS

approved

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Last modified December 1 17:49 EST 2022. Contains 358475 sequences. (Running on oeis4.)