A038394 Concatenate first n primes in reverse order.

2, 32, 532, 7532, 117532, 13117532, 1713117532, 191713117532, 23191713117532, 2923191713117532, 312923191713117532, 37312923191713117532, 4137312923191713117532, 434137312923191713117532, 47434137312923191713117532, 5347434137312923191713117532

Offset

1,1

References

F. Smarandache, Sequences of Numbers Involved in Unsolved Problems, Hexis, Phoenix, 2006.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..300

Mihaly Bencze [Beneze] and Lucian Tutescu, editors, Some Notions and Questions in Number Theory, Vol. II.

Micha Fleuren, Smarandache Back Concatenated Primes.

Florentin Smarandache, Sequences of Numbers Involved in Unsolved Problems.

Mathematica

Join[{s = 2}, Table[s = FromDigits[Flatten[IntegerDigits[{Prime[n], s}]]], {n, 2, 13}]] (* Jayanta Basu, Jul 14 2013 *)
With[{nn=20}, {prs=Prime[Range[nn]]}, Table[FromDigits[Flatten[IntegerDigits/@Reverse[Take[prs, n]]]], {n, nn}]] (* Harvey P. Dale, Jan 31 2026 *)

Prog

(Haskell)
a038394 n = a038394_list !! (n-1)
a038394_list = f "" a000040_list where
   f xs (q:qs) = (read ys :: Integer) : f ys qs
     where ys = show q ++ xs
-- Reinhard Zumkeller, Mar 03 2014
(PARI) a(n) = fromdigits(concat([digits(p) | p<-Vecrev(primes(n))])); \\ Andrew Howroyd, Aug 29 2020

Crossrefs

Cf. A000040, A000422, A019518.

Sequence in context: A010045 A052151 A092844 * A068110 A304860 A198599

Adjacent sequences: A038391 A038392 A038393 * A038395 A038396 A038397

Keyword

nonn,base

Author

M. I. Petrescu (mipetrescu(AT)yahoo.com)

Extensions

Offset corrected by Reinhard Zumkeller, Mar 03 2014

Status

approved