A114145 Self-describing sequence : 2 composite integers between two primes, then 4 composites, then 6, then 7, then 8, etc. The quantity of composites in each run is given by the sequence itself. (Sequence is strictly increasing and the smallest next available prime is used when needed).

2, 4, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 18, 20, 21, 23, 24, 25, 26, 27, 28, 30, 32, 37, 38, 39, 40, 42, 44, 45, 46, 48, 53, 54, 55, 56, 57, 58, 60, 62, 63, 64, 67, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 83, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 102

Offset

2,1

Links

Table of n, a(n) for n=2..72.

Example

Runs of composites between brackets:
2,(4,6),7,(8,9,10,12),13,(14,15,16,18,20,21),23,(24,25,26,27,28,30,32)...
.^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
.2 comp. 4 comp. 6 comp. 7 comp. (etc.) = the sequence itself

Prog

(PARI) {m=20; k=2; v=[k]; for(j=1, m, count=0; while(count<v[j], if(!isprime(k), v=concat(v, k); count++); k++); k=nextprime(k); v=concat(v, k)); for(n=1, #v, print1(v[n], ", "))} \\ Klaus Brockhaus

Crossrefs

Sequence in context: A015860 A147613 A155939 * A153351 A153343 A136499

Adjacent sequences: A114142 A114143 A114144 * A114146 A114147 A114148

Keyword

base,easy,nonn

Author

Eric Angelini, Feb 03 2006

Status

approved