OFFSET

1,1

COMMENTS

In Math. Mag. 48 (1975) 301 one finds "C. W. Trigg, C. C. Oursler and R. Cormier and J. L. Selfridge have sent calculations on Problem 886 [Nov 1973] for which we had received only partial results [Jan 1975]. Cormier and Selfridge sent the following results: There appear to be five sequences beginning with integers less than 1000 which do not merge. These sequences were carried out to 10^8 or more." The five sequences are A003508, A105210-A105213.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..2000

Doug Engel, Problem 886, Math. Mag., 48 (1975), 57-58.

EXAMPLE

a(2)=518 because a(1)=412, the distinct prime factors of a(1) are 2 and 103; finally, 1 + 412 + 2 + 103 = 518.

MAPLE

with(numtheory): p:=proc(n) local nn, ct, s: if isprime(n)=true then s:=0 else nn:=convert(factorset(n), list): ct:=nops(nn): s:=sum(nn[j], j=1..ct):fi: end: a[1]:=412: for n from 2 to 50 do a[n]:=1+a[n-1]+p(a[n-1]) od:seq(a[n], n=1..50); # Emeric Deutsch, Apr 14 2005

MATHEMATICA

nxt[n_]:=n+1+Total[Select[Transpose[FactorInteger[n]][[1]], #<n&]]; NestList[ nxt, 412, 50] (* Harvey P. Dale, Sep 13 2013 *)

PROG

(Haskell)

a105211 n = a105211_list !! (n-1)

a105211_list = 412 : map

(\x -> x + 1 + sum (takeWhile (< x) $ a027748_row x)) a105211_list

-- Reinhard Zumkeller, Jan 15 2015

CROSSREFS

KEYWORD

nonn,easy

AUTHOR

R. K. Guy, Apr 14 2005

EXTENSIONS

More terms from Robert G. Wilson v and Emeric Deutsch, Apr 14 2005

STATUS

approved