login
Numbers with a sum of digits which is not 7-smooth.
1

%I #24 Oct 13 2022 11:36:54

%S 29,38,47,49,56,58,65,67,74,76,83,85,89,92,94,98,119,128,137,139,146,

%T 148,155,157,164,166,173,175,179,182,184,188,191,193,197,199,209,218,

%U 227,229,236,238,245,247,254,256,263

%N Numbers with a sum of digits which is not 7-smooth.

%F a(n) ~ n.

%e 2 + 9 = 11 which is not of the form 2^a*3^b*5^c*7^d, so 29 is in the sequence.

%o (PARI) smooth(n,s)=forprime(p=2,s,n/=p^valuation(n,p)); n==1

%o is(n)=!smooth(sumdigits(n),7)

%Y Cf. A087144.

%K nonn,easy,base

%O 1,1

%A _Charles R Greathouse IV_, Oct 13 2022