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A095248
a(n) = least k > 0 such that n-th partial sum is divisible by n if and only if n is not prime.
1
1, 2, 1, 4, 1, 3, 1, 3, 2, 2, 1, 3, 1, 3, 2, 2, 1, 3, 1, 3, 2, 2, 1, 3, 2, 2, 2, 2, 1, 3, 1, 3, 2, 2, 2, 2, 1, 3, 2, 2, 1, 3, 1, 3, 2, 2, 1, 3, 2, 2, 2, 2, 1, 3, 2, 2, 2, 2, 1, 3, 1, 3, 2, 2, 2, 2, 1, 3, 2, 2, 1, 3, 1, 3, 2, 2, 2, 2, 1, 3, 2, 2, 1, 3, 2, 2, 2, 2, 1, 3, 2, 2, 2, 2, 2, 2, 1, 3, 2, 2, 1, 3, 1, 3, 2
OFFSET
1,2
LINKS
EXAMPLE
n = 1 is not prime, k = 1 results in first partial sum 1 divisible by 1 as required, so a(1) = 1.
n = 2 is prime, k = 1 results in second partial sum 2 divisible by 2 and is excluded, but k = 2 results in second partial sum 3 not divisible by 2 as required, so a(2) = 2.
PROG
(PARI) {m=105; s=0; for(n=1, m, k=1; if(isprime(n), while((s+k)%n==0, k++), while((s+k)%n>0, k++)); print1(k, ", "); s=s+k)}
CROSSREFS
Sequence in context: A124331 A242885 A181157 * A122458 A329644 A256578
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Jun 17 2004
EXTENSIONS
Edited and extended by Klaus Brockhaus, Jun 19 2004
STATUS
approved