|
|
A158457
|
|
a(1)=1, a(n+1) is the largest nonprime < sum of digits of n and a(n).
|
|
1
|
|
|
1, 1, 1, 1, 4, 8, 12, 9, 16, 15, 6, 6, 8, 10, 4, 9, 15, 12, 10, 10, 1, 1, 4, 8, 12, 9, 16, 15, 15, 16, 9, 12, 6, 10, 6, 12, 10, 10, 10, 12, 6, 10, 6, 12, 10, 9, 18, 18, 20, 14, 9, 14, 10, 8, 16, 16, 16, 18, 21, 16, 12, 9, 16, 15, 15, 16, 18, 21, 16, 21, 9, 16, 15, 15, 16, 18, 21, 16, 21
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,5
|
|
LINKS
|
|
|
EXAMPLE
|
1, 1(<2=1+1), 1(<3=2+1), 1(<4=3+1), 4(<5=4+1), 8(<9=5+4), 12(<14=6+8), 9(<10=7+1+2), etc.
|
|
MAPLE
|
A007953 := proc(n) add(d, d=convert(n, base, 10)) ; end proc:
A158457 := proc(n) if n = 1 then 1; else for a from A007953(n-1)+A007953(procname(n-1))-1 by -1 do if not isprime(a) then return a; end if; end do; end if; end proc:
|
|
MATHEMATICA
|
lnp[{n_, a_}]:=Module[{sd=Total[IntegerDigits[n+1]]+Total[ IntegerDigits[ a]]-1}, While[PrimeQ[sd], sd--]; {n+1, sd}]; NestList[lnp, {0, 1}, 80][[All, 2]] (* Harvey P. Dale, May 28 2021 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,base,less
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|