Data commit

Task/Smith-numbers/Stata/smith-numbers.stata

@@ -0,0 +1,73 @@
+function factor(_n) {
+	n = _n
+	a = J(14, 2, .)
+	i = 0
+	if (mod(n, 2)==0) {
+		j = 0
+		while (mod(n, 2)==0) {
+			j++
+			n = n/2
+		}
+		i++
+		a[i,1] = 2
+		a[i,2] = j
+	}
+	for (k=3; k*k<=n; k=k+2) {
+		if (mod(n, k)==0) {
+			j = 0
+			while (mod(n, k)==0) {
+				j++
+				n = n/k
+			}
+			i++
+			a[i,1] = k
+			a[i,2] = j
+		}
+	}
+	if (n>1) {
+		i++
+		a[i,1] = n
+		a[i,2] = 1
+	}
+	return(a[1::i,.])
+}
+
+function sumdigits(_n) {
+	n = _n
+	for (s=0; n>0; n=floor(n/10)) s = s+mod(n,10)
+	return(s)
+}
+
+function smith(n) {
+	a = J(n, 1, .)
+	i = 0
+	for (j=2; j<=n; j++) {
+		f = factor(j)
+		m = rows(f)
+		if (m>1 | f[1,2]>1) {
+			s = 0
+			for (k=1; k<=m; k++) s = s+sumdigits(f[k,1])*f[k,2]
+			if (s==sumdigits(j)) a[++i] = j
+		}
+	}
+	return(a[1::i])
+}
+
+a = smith(10000)
+n = rows(a)
+n
+  376
+
+a[1::10]'
+
+         1     2     3     4     5     6     7     8     9    10
+    +-------------------------------------------------------------+
+  1 |    4    22    27    58    85    94   121   166   202   265  |
+    +-------------------------------------------------------------+
+
+a[n-9::n]'
+
+          1      2      3      4      5      6      7      8      9     10
+    +-----------------------------------------------------------------------+
+  1 |  9843   9849   9861   9880   9895   9924   9942   9968   9975   9985  |
+    +-----------------------------------------------------------------------+