OFFSET
1,2
FORMULA
a(n) = A028834(n) - 1.
MAPLE
P:=proc(n) local i, k, w; for i from 1 by 1 to n do w:=0; k:=binomial(i+1, i); while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; if isprime(w) then print(i); fi; od; end: P(1000);
MATHEMATICA
Select[Range[200], PrimeQ[Total[IntegerDigits[# + 1]]] &]
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Paolo P. Lava and Giorgio Balzarotti, May 31 2007
STATUS
approved