A344860 - OEIS

%I #11 May 31 2021 21:32:39

%S 192,238,250,293,312,346,382,432,436,446,465,510,544,554,560,571,578,

%T 583,593,607,609,631,658,671,727,729,771,780,803,812,825,844,845,848,

%U 860,866,877,883,894,917,945,962,967,974,991,1000,1004,1031,1042,1052,1061

%N Numbers k such that A306920(k) contains the digit 0 and A306920(k+1) is not A306920(k) with a digit 0 removed.

%e A306920(192) = 1021, containing the digit 0, A306920(193) = 1039 and 1039 cannot be obtained by removing a 0 digit from 1021, so 192 is a term of the sequence.

%o (PARI) eva(n) = subst(Pol(n), x, 10)

%o insert(n, len, pos) = my(d=digits(n), v=[], w=[]); for(y=1, pos, v=concat(v, d[y])); v=concat(v, vector(len)); for(z=pos+1, #d, v=concat(v, d[z])); eva(v)

%o a306920(n) = forprime(p=10, , for(k=1, #digits(p)-1, my(zins=insert(p, n, k)); if(ispseudoprime(zins), return(p))))

%o remove_zeros(n) = my(v=[], w=[], d=digits(n)); for(x=1, #d, if(d[x]==0, for(y=1, x-1, w=concat(w, d[y])); for(z=x+1, #d, w=concat(w, d[z]))); if(#w > 0, v=concat(v, [eva(w)])); w=[]); vecsort(v, , 8)

%o is(n) = my(x=a306920(n), y=a306920(n+1), rz=remove_zeros(x)); if(#setintersect([0], vecsort(digits(x)))==0, return(0)); for(k=1, #rz, if(y==rz[k], return(0))); 1

%Y Cf. A306920, A306926.

%K nonn,base

%O 1,1

%A _Felix Fröhlich_, May 31 2021