A097515 - OEIS

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A097515

a(n) = (largest prime < 10^n) + (smallest prime > 10^n).

18, 198, 2006, 19980, 199994, 1999986, 20000010, 199999996, 1999999944, 19999999986, 199999999980, 2000000000028, 20000000000008, 200000000000004, 2000000000000026, 19999999999999998, 200000000000000000, 1999999999999999992, 20000000000000000012, 200000000000000000028

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OFFSET

1,1

LINKS

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

FORMULA

a(n) = A003618(n) + A003617(n+1). - Amiram Eldar, Jul 02 2024

MATHEMATICA

Table[NextPrime[10^n, -1]+NextPrime[10^n], {n, 20}] (* Harvey P. Dale, May 03 2018 *)

CROSSREFS

Cf. A003617, A003618.

Sequence in context: A020920 A083812 A086573 * A177358 A026881 A181961