login
A226521
Triangle read by rows: T(n,k) = smallest prime == k (mod n) if gcd(k,n)=1, otherwise 0, for n >= 2, 1 <= k < n.
0
3, 7, 2, 5, 0, 3, 11, 2, 3, 19, 7, 0, 0, 0, 5, 29, 2, 3, 11, 5, 13, 17, 0, 3, 0, 5, 0, 7, 19, 2, 0, 13, 5, 0, 7, 17, 11, 0, 3, 0, 0, 0, 7, 0, 19, 23, 2, 3, 37, 5, 17, 7, 19, 31, 43, 13, 0, 0, 0, 5, 0, 7, 0, 0, 0, 11, 53, 2, 3, 17, 5, 19, 7, 47, 61, 23, 11, 103, 29, 0, 3, 0, 5, 0, 0, 0, 23, 0, 11, 0, 13, 31, 2, 0, 19, 0, 0, 7, 23, 0, 0, 11, 0, 13, 29
OFFSET
2,1
REFERENCES
Elliott, P. D. T. A.; Halberstam, H. The least prime in an arithmetic progression, 1971; Studies in Pure Mathematics (Presented to Richard Rado) pp. 59--61, Academic Press, London MR0272728 (42 #7609)
EXAMPLE
Triangle begins:
3;
7, 2;
5, 0, 3;
11, 2, 3, 19;
7, 0, 0, 0, 5;
29, 2, 3, 11, 5, 13;
17, 0, 3, 0, 5, 0, 7;
19, 2, 0, 13, 5, 0, 7, 17;
11, 0, 3, 0, 0, 0, 7, 0, 19;
...
MAPLE
for n from 2 to 15 do
a:=Array(1..n-1);
for k from 1 to n-1 do
if gcd(n, k)=1 then
p:=k;
for j from 1 to 100 do
if isprime(p) then break; fi;
p:=n+p;
od:
a[k]:=p;
fi;
od:
lprint([seq(a(k), k=1..n-1)]);
od:
CROSSREFS
Sequence in context: A334959 A064824 A336893 * A091723 A274509 A016618
KEYWORD
nonn,tabl
AUTHOR
N. J. A. Sloane, Jun 20 2013
STATUS
approved