A276939 Row 2 of A276945: a(n) = A002110(n) + A002110(n+1).

3, 8, 36, 240, 2520, 32340, 540540, 10210200, 232792560, 6692786100, 207030183360, 7621298624940, 311671001662020, 13387011595197240, 627972543920161440, 33204048259778536140, 1955349508631402683800, 119211141709561183622340, 7975609932439674026862360, 565799151677779228023294480, 41287621429375723111588738860

Offset: 0

Author

Antti Karttunen, Sep 24 2016

Keywords

• nonn
• base

Comments

a(n) = number whose primorial base representation (A049345) begins with digits "11", followed by n zeros: 11, 110, 1100, 11000, 110000, ...

Links

• Michael De Vlieger, Table of n, a(n) for n = 0..349
• Index entries for sequences related to primorial base

Crossrefs

Row 2 of A276945 (column 2 of A276943).

Cf. A002110, A049345.

Programs

Mathematica

Total /@ Partition[FoldList[Times, 1, Prime@ Range[20]], 2, 1] (* Michael De Vlieger, Jun 24 2023 *)

PARI

a(n) = factorback(primes(n)) + factorback(primes(n+1)); \\ Michel Marcus, Nov 23 2022

Scheme

(define (A276939 n) (+ (A002110 n) (A002110 (+ 1 n))))

Formula

a(n) = A002110(n) + A002110(n+1).