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Number of i such that d(i) < d(i-1), where Sum_{i=0..m} d(i)*7^i is the base-7 representation of n.
2

%I #15 Jul 23 2023 18:24:44

%S 0,0,0,0,0,0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,0,0,0,0,1,1,1,0,0,0,0,0,1,1,

%T 0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,1,1,1,1,1,1,0,0,1,1,1,1,1,1,1,1,2,2,2,

%U 2,1,1,1,1,2,2,2,1,1,1,1,1,2,2,1,1,1,1,1,1,2

%N Number of i such that d(i) < d(i-1), where Sum_{i=0..m} d(i)*7^i is the base-7 representation of n.

%p A037805 := proc(n)

%p a := 0 ;

%p dgs := convert(n,base,7);

%p for i from 2 to nops(dgs) do

%p if op(i,dgs)<op(i-1,dgs) then

%p a := a+1 ;

%p end if;

%p end do:

%p a ;

%p end proc: # _R. J. Mathar_, Oct 16 2015

%o (PARI) a(n) = {my(d = Vecrev(digits(n, 7))); my(dd = vector(#d-1, k, d[k+1] - d[k])); #select(x->(x<0), dd);} \\ _Michel Marcus_, Oct 16 2015

%Y Cf. A037822.

%K nonn,base

%O 1,66

%A _Clark Kimberling_

%E Sign in name corrected by _R. J. Mathar_, Oct 16 2015