A114147 Self-describing sequence : 1 prime between two nonprimes, then 2 primes between two nonprimes, then 4 primes, then 5, then 7, etc. The quantity of primes in each run is given by the sequence itself. (Sequence is strictly increasing and the smallest next available nonprime is used when needed).

1, 2, 4, 5, 7, 8, 11, 13, 17, 19, 20, 23, 29, 31, 37, 41, 42, 43, 47, 53, 59, 61, 67, 71, 72, 73, 79, 83, 89, 97, 101, 103, 107, 108, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 168, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 240, 241

Offset

1,2

Links

Table of n, a(n) for n=1..61.

Example

Runs of primes are between brackets:
1,(2),4,(5,7),8,(11,13,17,19),20,(23,29,31,37,41),42,(43,47,53,59,61,67,71)
.^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
1 prime 2 pr. 4 primes 5 primes 7 primes (etc.) = the sequence itself

Prog

(PARI) {m=10; k=1; v=[k]; for(j=1, m, for(count=1, v[j], k=nextprime(k+1); v=concat(v, k)); while(isprime(k), k++); v=concat(v, k)); for(n=1, #v, print1(v[n], ", "))} \\ Klaus Brockhaus

Crossrefs

Sequence in context: A076697 A001606 A014554 * A281276 A025516 A191174

Adjacent sequences: A114144 A114145 A114146 * A114148 A114149 A114150

Keyword

base,easy,nonn

Author

Eric Angelini and Alexandre Wajnberg

Status

approved